mb/intel/beechnutcity_crb: Add GNR/SRF-SP 2S server board Beechnut City

mb/intel/beechnutcity_crb: Add GNR/SRF-SP 2S server board Beechnut City

Beechnut City CRB is the 2 socket reference board for 6th Gen Xeon-SP
SP SoCs (Granite Rapids SP and Sierra Forest SP).

This patch initially sets the code set up as a compilation target with
GNR N-1 FSP, and with basic feature supports (Integrated IO Controller
(IIO) configuration, BMC, UART, HPET).

TEST=Build on intel/beechnutcity CRB

Change-Id: I3f6a0fb97b62baadb438fb9f11fdd78fccb3f89a
Signed-off-by: Shuo Liu <shuo.liu@intel.com>
Co-authored-by: Gang Chen <gang.c.chen@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81322
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>