drivers: firmware: ti_sci: Add DM_FLAG_PRE_RELOC to driver

drivers: firmware: ti_sci: Add DM_FLAG_PRE_RELOC to driver

Currently the driver relies on bootph flag to probe it during PRE_RELOC
stage but with the upcoming cleanup of v6.13, we don't have the bootph
property in the parent nodes anymore and ti_sci driver being one of the
parent nodes required during SPL stage would end up hampering the probe
model [0].

Add DM_FLAG_PRE_RELOC to ti_sci driver for mitigating this issue.

[0]: https://source.denx.de/u-boot/custodians/u-boot-dm/-/issues/21

Suggested-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Manorit Chawdhry <m-chawdhry@ti.com>