testsuite, X86: Fix missing U_L_P on pr126293-1b.c.

These new tests were failing on darwin because of the missing user
label prefix.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr126293-1b.c: Account for USER_LABEL_PREFIX.
	* gcc.target/i386/pr126293-1c.c: Likwise.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>