kfifo: fix KFIFO_INIT in include/linux/kfifo.h

include/linux/kfifo.h first defines and then undefines __kfifo_initializer
which is used by INIT_KFIFO (which is also a macro, so building a module
which uses INIT_KFIFO will fail).
Signed-off-by: David Härdeman <david@hardeman.nu>
Acked-by: Stefani Seibold <stefani@seibold.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kfifo.h

@@ -102,8 +102,6 @@ union { \
 	unsigned char name##kfifo_buffer[size]; \
 	struct kfifo name = __kfifo_initializer(size, name##kfifo_buffer)
 
-#undef __kfifo_initializer
-
 extern void kfifo_init(struct kfifo *fifo, void *buffer,
 			unsigned int size);
 extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,