x86/retpoline: Add ANNOTATE_NOENDBR for retpolines

The retpolines are exported, so they're referenced by ksymtab sections.
But they're never indirect-branched to, so add ANNOTATE_NOENDBR.

Fixes: ed53a0d9 ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/b6ec963dfd9301b6b1d74ef7758fcb0b540d6c6c.1650300597.git.jpoimboe@redhat.com

arch/x86/lib/retpoline.S

@@ -31,6 +31,7 @@
 	.align RETPOLINE_THUNK_SIZE
 SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
 	UNWIND_HINT_EMPTY
+	ANNOTATE_NOENDBR
 
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
 		      __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \
@@ -55,7 +56,6 @@ SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
 
 	.align RETPOLINE_THUNK_SIZE
 SYM_CODE_START(__x86_indirect_thunk_array)
-	ANNOTATE_NOENDBR // apply_retpolines
 
 #define GEN(reg) THUNK reg
 #include <asm/GEN-for-each-reg.h>