mb/google/brya: Use default EPP of 50% for skolas

mb/google/brya: Use default EPP of 50% for skolas

A power and performance analysis performed on Alder Lake demonstrated
that with an EPP (Energy Performance Preference) at 50% along with
EET (Energy Efficient Turbo) disabled, the overall SoC performance are
similar or better and the SoC uses less power.

For instance some browser benchmark results improved by 2% and some
multi-core tests by 4% while at the same time power consumption
lowered by approximately 7.6%.

Similar results are observed on Raptor Lake.

BRANCH=firmware-brya-14505.B
BUG=b:240669428
TEST=verify that EPP is back to the by default 50% setting
     `iotools rdmsr 0 0x774'

Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Change-Id: I735ad9d88c7bf54def7a23b75abc4e89a213fb61
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66282
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Zhixing Ma <zhixing.ma@intel.com>
Reviewed-by: Selma Bensaid <selma.bensaid@intel.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>