[IA64] remove BUILD_BUG_ON from paravirt_getreg()

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'

Obvious inclusion of kernel.h doesn't fix it, because of circular dependencies
involving fls.h and log2(). Fixing the latter requires some serious header surgery,
it seems, so just remove BUILD_BUG_ON for now.

Signed-off-by: Alexey Dobriyan <[e-mail]>
Signed-off-by: Tony Luck <[e-mail]>

arch/ia64/include/asm/paravirt_privop.h

···
 #define paravirt_getreg(reg)					\
 	({							\
 		unsigned long res;				\
-		BUILD_BUG_ON(!__builtin_constant_p(reg));	\
 		if ((reg) == _IA64_REG_IP)			\
 			res = ia64_native_getreg(_IA64_REG_IP); \
 		else						\