mb/ocp: Remove superfluous FSP header CPP inclusion

This is already done in drivers/intel/fsp2_0/Makefile.inc.

Change-Id: Idfd15d0a9d2cb15e613881f80bb25c18bd7454bb
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57484
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/soc/intel/xeon_sp/Makefile.inc

@@ -19,6 +19,5 @@ postcar-y += spi.c
 subdirs-$(CONFIG_SOC_INTEL_XEON_RAS) += ras
 
 CPPFLAGS_common += -I$(src)/soc/intel/xeon_sp/include
-CPPFLAGS_common += -I$(CONFIG_FSP_HEADER_PATH)
 
 endif ## XEON_SP_COMMON_BASE