nb/intel: Remove unused 'barrier()'

Change-Id: I0c33a1f3f9c33c15a901fe90258ed989e9641701
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36124
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/northbridge/intel/haswell/haswell.h

@@ -202,7 +202,6 @@
 #define DMIDRCCFG	0xeb4	/* 32bit */
 
 #ifndef __ASSEMBLER__
-static inline void barrier(void) { asm("" ::: "memory"); }
 
 void intel_northbridge_haswell_finalize_smm(void);