[S390] correct alignment of cpuid structure

The store-cpu-id instruction has a minimum alignment of 8. Reflect
that in the definition of struct cpuid.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/cpu.h

@@ -20,7 +20,7 @@ struct cpuid
 	unsigned int ident   : 24;
 	unsigned int machine : 16;
 	unsigned int unused  : 16;
-} __packed;
+} __attribute__ ((packed, aligned(8)));
 
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_S390_CPU_H */