MIPS: Makefile: Move the ASEs checks after setting the core's CFLAGS

We need to check the ASEs support against the core's CFLAGS instead
of depending to the default -march option from the toolchain.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9180/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>