mb/google/rex/var/rex0: Refactor SSD power sequencing

Improve SSD readiness time by enabling earlier power sequencing.

Here are the two GPIOs to look for:
* GPP_A19: Power Enable
* GPP_A20: PERST

The flow is presented as `stage (GPIO PAD/Value)` for easy
understanding:

bootblock (A20/0, A19/1)
|
v
romstage (A20/1)

Ideally, we don't need SSD power sequencing at ramstage, hence, remove
the logic from ramstage.

TEST=Able to build and boot google/rex0 using NVMe without any problems.
S0ix and read/write from/to SSD are also normal.

Change-Id: Idde2f7693771f1d7e3171e51232d1bb899bfe33e
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80641
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

0 files changed, 0 insertions, 0 deletions