sparc: asm/bitops.h should define __fls

bitops_64.h includes the generic one; pretty sure 32 should too.

(Found by using __fls in generic code and breaking sparc defconfig build:
 thanks Stephen and linux-next!)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>