gpio: 74x164: use dev_read_* APIs for live-tree compatibility

gpio: 74x164: use dev_read_* APIs for live-tree compatibility

With CONFIG_OF_LIVE=y, dev_of_offset(dev) does not return a valid
flat-FDT offset, so fdtdec_get_int(gd->fdt_blob, offset, ...) inside
gen_74x164_probe() fails to locate the "registers-number" property and
always falls back to the default value of 1. This results in a 4-chip
74HC595 daisy chain being exposed as only 8 GPIOs instead of 32, and
any consumer referencing offsets >= 8 fails to bind with -ENOENT
("GPIO ... not found" / Error -22).

The "registers-default" property is ignored for the same reason, so
any configured power-on output pattern is silently discarded.

Replace the flat-FDT helpers with dev_read_u32_default() and
dev_read_u8_array_ptr(), which correctly walk both live and flat
trees. This matches how other DM GPIO drivers (e.g. pca953x_gpio.c)
read their per-device properties.

With gd->fdt_blob no longer referenced, also drop the now-unused
DECLARE_GLOBAL_DATA_PTR and <asm/global_data.h> include.

Tested on stm32mp153d-ssonic (CONFIG_OF_LIVE=y) with a 4-chip 74HC595
chain: all 32 GPIOs are now exposed, and 16 consumer LED nodes at
offsets 0..31 bind successfully.

Fixes: 9300f711baac ("dm: gpio: introduce 74x164 driver")
Signed-off-by: Chanhong Jung <happycpu@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>