objtool: whitelist __sanitizer_cov_trace_switch()

it's not really different from e.g. __sanitizer_cov_trace_cmp4();
as it is, the switches that generate an array of labels get
rejected by objtool, while slightly different set of cases
that gets compiled into a series of comparisons is accepted.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

tools/objtool/check.c

@@ -478,6 +478,7 @@ static const char *uaccess_safe_builtin[] = {
 	"__sanitizer_cov_trace_cmp2",
 	"__sanitizer_cov_trace_cmp4",
 	"__sanitizer_cov_trace_cmp8",
+	"__sanitizer_cov_trace_switch",
 	/* UBSAN */
 	"ubsan_type_mismatch_common",
 	"__ubsan_handle_type_mismatch",