objtool: Fix another switch table detection issue

Continue the switch table detection whack-a-mole. Add a check to
distinguish KASAN data reads from switch data reads. The switch jump
tables in .rodata have relocations associated with them.

This fixes the following warning:

crypto/asymmetric_keys/x509_cert_parser.o: warning: objtool: x509_note_pkey_algo()+0xa4: sibling call from callable instruction with modified stack frame

Reported-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Josh Poimboeuf <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Tested-by: Arnd Bergmann <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]

tools/objtool/check.c

···
 		if (find_symbol_containing(file->rodata, text_rela->addend))
 			continue;
 
-		return find_rela_by_dest(file->rodata, text_rela->addend);
+		rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend);
+		if (!rodata_rela)
+			continue;
+
+		return rodata_rela;
 	}
 
 	return NULL;