serdev: Convert to_serdev_*() helpers to macros and use container_of_const()

serdev: Convert to_serdev_*() helpers to macros and use container_of_const()

If these helpers receive the 'const struct device' pointer, then the const
qualifier will get dropped, leading to below warning:

warning: passing argument 1 of ‘to_serdev_device_driver’ discards 'const'
qualifier from pointer target type [-Wdiscarded-qualifiers]

This is not an issue as of now, but with the future commits adding serdev
device based driver matching, this warning will get triggered. Hence,
convert these helpers to macros so that the qualifier get preserved and
also use container_of_const() as container_of() is deprecated.

Tested-by: Hans de Goede <johannes.goede@oss.qualcomm.com> # ThinkPad T14s gen6 (arm64)
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260326-pci-m2-e-v7-1-43324a7866e6@oss.qualcomm.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>