pinctrl: s32cc: fix uninitialized memory in s32_pinctrl_desc

pinctrl: s32cc: fix uninitialized memory in s32_pinctrl_desc

s32_pinctrl_desc is allocated with devm_kmalloc(), but not all of its
fields are initialized. Notably, num_custom_params is used in
pinconf_generic_parse_dt_config(), resulting in intermittent allocation
errors, such as the following splat when probing i2c-imx:

        WARNING: CPU: 0 PID: 176 at mm/page_alloc.c:4795 __alloc_pages_noprof+0x290/0x300
        [...]
        Hardware name: NXP S32G3 Reference Design Board 3 (S32G-VNP-RDB3) (DT)
        [...]
        Call trace:
         __alloc_pages_noprof+0x290/0x300 (P)
         ___kmalloc_large_node+0x84/0x168
         __kmalloc_large_node_noprof+0x34/0x120
         __kmalloc_noprof+0x2ac/0x378
         pinconf_generic_parse_dt_config+0x68/0x1a0
         s32_dt_node_to_map+0x104/0x248
         dt_to_map_one_config+0x154/0x1d8
         pinctrl_dt_to_map+0x12c/0x280
         create_pinctrl+0x6c/0x270
         pinctrl_get+0xc0/0x170
         devm_pinctrl_get+0x50/0xa0
         pinctrl_bind_pins+0x60/0x2a0
         really_probe+0x60/0x3a0
        [...]
         __platform_driver_register+0x2c/0x40
         i2c_adap_imx_init+0x28/0xff8 [i2c_imx]
        [...]

This results in later parse failures that can cause issues in dependent
drivers:

        s32g-siul2-pinctrl 4009c240.pinctrl: /soc@0/pinctrl@4009c240/i2c0-pins/i2c0-grp0: could not parse node property
        s32g-siul2-pinctrl 4009c240.pinctrl: /soc@0/pinctrl@4009c240/i2c0-pins/i2c0-grp0: could not parse node property
        [...]
        pca953x 0-0022: failed writing register: -6
        i2c i2c-0: IMX I2C adapter registered
        s32g-siul2-pinctrl 4009c240.pinctrl: /soc@0/pinctrl@4009c240/i2c2-pins/i2c2-grp0: could not parse node property
        s32g-siul2-pinctrl 4009c240.pinctrl: /soc@0/pinctrl@4009c240/i2c2-pins/i2c2-grp0: could not parse node property
        i2c i2c-1: IMX I2C adapter registered
        s32g-siul2-pinctrl 4009c240.pinctrl: /soc@0/pinctrl@4009c240/i2c4-pins/i2c4-grp0: could not parse node property
        s32g-siul2-pinctrl 4009c240.pinctrl: /soc@0/pinctrl@4009c240/i2c4-pins/i2c4-grp0: could not parse node property
        i2c i2c-2: IMX I2C adapter registered

Fix this by initializing s32_pinctrl_desc with devm_kzalloc() instead of
devm_kmalloc() in s32_pinctrl_probe(), which sets the previously
uninitialized fields to zero.

Fixes: fd84aaa8173d ("pinctrl: add NXP S32 SoC family support")
Signed-off-by: Jared Kangas <jkangas@redhat.com>
Tested-by: Jan Petrous (OSS) <jan.petrous@oss.nxp.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>