support multiple .discard.* sections to avoid section type conflicts

gcc 4.4.4 will complain if you use a .discard section for both text and
data ("causes a section type conflict").  Add support for ".discard.*"
sections, and use .discard.text for a dummy function in the x86
RESERVE_BRK() macro.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

arch/x86/include/asm/setup.h

@@ -82,7 +82,7 @@ void *extend_brk(size_t size, size_t align);
  * executable.)
  */
 #define RESERVE_BRK(name,sz)						\
-	static void __section(.discard) __used				\
+	static void __section(.discard.text) __used			\
 	__brk_reservation_fn_##name##__(void) {				\
 		asm volatile (						\
 			".pushsection .brk_reservation,\"aw\",@nobits;" \

include/asm-generic/vmlinux.lds.h

@@ -643,6 +643,7 @@
 	EXIT_DATA							\
 	EXIT_CALL							\
 	*(.discard)							\
+	*(.discard.*)							\
 	}
 
 /**