MIPS: Makefile: Fix MIPS ASE detection code

MIPS: Makefile: Fix MIPS ASE detection code

Commit 32098ec7bcba ("MIPS: Makefile: Move the ASEs checks after
setting the core's CFLAGS") re-arranged the MIPS ASE detection code
and also added the current cflags to the detection logic. However,
this introduced a few bugs. First of all, the mips-cflags should not
be quoted since that ends up being passed as a string to subsequent
commands leading to broken detection from the cc-option-* tools.
Moreover, in order to avoid duplicating the cflags-y because of how
cc-option works, we rework the logic so we pass only those cflags which
are needed by the selected ASE. Finally, fix some typos resulting in MSA
not being detected correctly.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Fixes: Commit 32098ec7bcba ("MIPS: Makefile: Move the ASEs checks after setting the core's CFLAGS")
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9661/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>