arch/x86/cpu.c: Remove redundant <arch/cpu.h>

<arch/cpu.h> is chain included through <cpu/cpu.h>.

Change-Id: Iad7f23080814c6606603d9472a1bd34a6b1bd1a9
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50304
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/x86/cpu.c

@@ -9,7 +9,6 @@
 #include <cpu/x86/mp.h>
 #include <cpu/x86/lapic.h>
 #include <cpu/x86/tsc.h>
-#include <arch/cpu.h>
 #include <device/path.h>
 #include <device/device.h>
 #include <smp/spinlock.h>