linux/compiler.h: don't use bool

Appararently, it's possible to have a non-trivial TU include a few
headers, including linux/build_bug.h, without ending up with
linux/types.h.  So the 0day bot sent me

config: um-x86_64_defconfig (attached as .config)

>> include/linux/compiler.h:316:3: error: unknown type name 'bool'; did you mean '_Bool'?
      bool __cond = !(condition);    \

for something I'm working on.

Rather than contributing to the #include madness and including
linux/types.h from compiler.h, just use int.

Link: http://lkml.kernel.org/r/20180817101036.20969-1-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Christopher Li <sparse@chrisli.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/compiler.h

@@ -313,7 +313,7 @@ unsigned long read_word_at_a_time(const void *addr)
 #ifdef __OPTIMIZE__
 # define __compiletime_assert(condition, msg, prefix, suffix)		\
 	do {								\
-		bool __cond = !(condition);				\
+		int __cond = !(condition);				\
 		extern void prefix ## suffix(void) __compiletime_error(msg); \
 		if (__cond)						\
 			prefix ## suffix();				\