Fix gdb.base/msym*.exp failures

Fix gdb.base/msym*.exp failures

AArch64 generates functions without a prologue for these two testcases,
therefore we shouldn't expect the function location to be displayed with
an offset.

gdb/testsuite/ChangeLog:

2020-10-22  Luis Machado  <luis.machado@linaro.org>

	* gdb.base/msym-bp-shl.exp (test_break): Adjust pattern to not
	expected an offset from the function.
	* gdb.base/msym-bp.exp (test): Likewise.