[ARM] Add warning about building fiq.c with gcc >= 3.4

Unfortunately, some changes to GCC prevents fiq.c expressing the
constraints for the assembly setting the FIQ register set.  Warn
people with later gcc toolchains that they can expect failure to
occur.
Signed-off-by: Russell King <rmk@arm.linux.org.uk>

arch/arm/kernel/fiq.c

@@ -46,6 +46,12 @@
 #include <asm/system.h>
 #include <asm/uaccess.h>
 
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+#warning This file requires GCC 3.3.x or older to build.  Alternatively,
+#warning please talk to GCC people to resolve the issues with the
+#warning assembly clobber list.
+#endif
+
 static unsigned long no_fiq_insn;
 
 /* Default reacquire function