kernel.h: Silence sparse warning in lower_32_bits

I keep getting sparse warnings in crypto such as:

  CHECK   drivers/crypto/ccree/cc_hash.c
   drivers/crypto/ccree/cc_hash.c:49:9: warning: cast truncates bits from constant value (47b5481dbefa4fa4 becomes befa4fa4)
   drivers/crypto/ccree/cc_hash.c:49:26: warning: cast truncates bits from constant value (db0c2e0d64f98fa7 becomes 64f98fa7)
   [.. many more ..]

This patch removes the warning by adding a mask to keep sparse
happy.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kernel.h

@@ -186,7 +186,7 @@
  * lower_32_bits - return bits 0-31 of a number
  * @n: the number we're accessing
  */
-#define lower_32_bits(n) ((u32)(n))
+#define lower_32_bits(n) ((u32)((n) & 0xffffffff))
 
 struct completion;
 struct pt_regs;