x86/retpoline: Move the retpoline thunk declarations to nospec-branch.h

Because it makes no sense to split the retpoline gunk over multiple
headers.

Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Reviewed-by: Borislav Petkov <[e-mail]>
Acked-by: Josh Poimboeuf <[e-mail]>
Tested-by: Alexei Starovoitov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/x86/include/asm/asm-prototypes.h

···
 extern void cmpxchg8b_emu(void);
 #endif
 
-#ifdef CONFIG_RETPOLINE
-
-#define GEN(reg) \
-	extern asmlinkage void __x86_indirect_thunk_ ## reg (void);
-#include <asm/GEN-for-each-reg.h>
-#undef GEN
-
-#endif /* CONFIG_RETPOLINE */

arch/x86/include/asm/nospec-branch.h

···
 
 #include <linux/static_key.h>
 #include <linux/objtool.h>
+#include <linux/linkage.h>
 
 #include <asm/alternative.h>
 #include <asm/cpufeatures.h>
···
 	".popsection\n\t"
 
 #ifdef CONFIG_RETPOLINE
+
+#define GEN(reg) \
+	extern asmlinkage void __x86_indirect_thunk_ ## reg (void);
+#include <asm/GEN-for-each-reg.h>
+#undef GEN
+
 #ifdef CONFIG_X86_64
 
 /*

arch/x86/net/bpf_jit_comp.c

···
 #include <asm/set_memory.h>
 #include <asm/nospec-branch.h>
 #include <asm/text-patching.h>
-#include <asm/asm-prototypes.h>
 
 static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
 {