target-mips: fix call to check_*() functions

check_*() functions may in fine call generate_exception(), which ends
by a call to tcg_gen_exit_tb(). As a consequence, we have to make sure
that no TCG temp variables are crossing a check_*() function.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7127 c046a42c-6fe2-441c-8c8c-71466251a162
