bug.h: add include of it to various implicit C users

With bug.h currently living right in linux/kernel.h there
are files that use BUG_ON and friends but are not including
the header explicitly.  Fix them up so we can remove the
presence in kernel.h file.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

arch/powerpc/kernel/pmc.c

@@ -13,6 +13,7 @@
  */
 
 #include <linux/errno.h>
+#include <linux/bug.h>
 #include <linux/spinlock.h>
 #include <linux/export.h>