soc/intel/common/cpu: Use SoC overrides to set CPU privilege level

This patch implements a SoC overrides to set CPU privilege level
as the MSR is not consistent across platforms. For example:
On APL/GLK/DNV, it's MSR 0x120 and CNL onwards it's MSR 0x151.

BUG=b:233199592
TEST=Build and boot google/taeko to ChromeOS.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I4584516102560e6bb2a4ae8c0d036be40ed96990
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64806
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>

src/soc/intel/apollolake/cpu.c

@@ -54,6 +54,15 @@ bool cpu_soc_is_in_untrusted_mode(void)
 	return !!(msr.lo & ENABLE_IA_UNTRUSTED);
 }
 
+void cpu_soc_bios_done(void)
+{
+	msr_t msr;
+
+	msr = rdmsr(MSR_POWER_MISC);
+	msr.lo |= ENABLE_IA_UNTRUSTED;
+	wrmsr(MSR_POWER_MISC, msr);
+}
+
 void soc_core_init(struct device *cpu)
 {
 	/* Configure Core PRMRR for SGX. */