[IA64] fix allmodconfig compilation breakage.

This patch fixes the following compilation error caused by recursive
inclusion of kernel.h which defines BUILD_BUG_ON().
In this case, the case it catches will be caught by the case
CONFIG_PARAVIRT=n, so removing it would not hurt compile time check
very much. So fix the breakage by removing it.

CC arch/ia64/kernel/asm-offsets.s
In file included from include/linux/bitops.h:17,
from include/linux/kernel.h:15,
from include/linux/sched.h:52,
from arch/ia64/kernel/asm-offsets.c:9:
arch/ia64/include/asm/bitops.h: In function 'set_bit':
arch/ia64/include/asm/bitops.h:47: error: implicit declaration of function 'BUILD_BUG_ON'

Signed-off-by: Isaku Yamahata <[e-mail]>
Signed-off-by: Tony Luck <[e-mail]>

arch/ia64/include/asm/paravirt_privop.h

···
 		register unsigned long ia64_intri_res asm ("r8");	\
 		register unsigned long __reg asm ("r8") = (reg);	\
 									\
-		BUILD_BUG_ON(!__builtin_constant_p(reg));		\
 		asm volatile (paravirt_alt_bundle(__PARAVIRT_BR,	\
 						  PARAVIRT_TYPE(GETREG) \
 						  + (reg))		\
···
 		register unsigned long ia64_clobber1 asm ("r8");	\
 		register unsigned long ia64_clobber2 asm ("r9");	\
 									\
-		BUILD_BUG_ON(!__builtin_constant_p(reg));		\
 		asm volatile (paravirt_alt_bundle(__PARAVIRT_BR,	\
 						  PARAVIRT_TYPE(SETREG) \
 						  + (reg))		\