h8300: IRQ flags should be stored in an unsigned long

Fix h8300's asm/atomic.h to store the IRQ flags in an unsigned long to deal
with warnings of the following type:

  arch/h8300/include/asm/atomic.h: In function 'atomic_add_return':
  arch/h8300/include/asm/atomic.h:22: warning: comparison of distinct pointer types lacks a cast
  arch/h8300/include/asm/atomic.h:24: warning: comparison of distinct pointer types lacks a cast

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>