tcg/mips: Fix build error from merged memop+mmu_idx parameter

tcg/mips: Fix build error from merged memop+mmu_idx parameter

Commit 3972ef6f830d ("tcg: Push merged memop+mmu_idx parameter to
softmmu routines") caused the following build errors when building TCG
for MIPS:

In file included from tcg/tcg.c:258:0:
tcg/mips/tcg-target.c In function ‘tcg_out_qemu_ld_slow_path’:
tcg/mips/tcg-target.c:1015:22: error: ‘lb’ undeclared (first use in this function)
tcg/mips/tcg-target.c In function ‘tcg_out_qemu_st_slow_path’:
tcg/mips/tcg-target.c:1058:22: error: ‘lb’ undeclared (first use in this function)

It looks like lb was meant to refer to the TCGLabelQemuLdst *l
parameter, so fix both references to lb to refer to just l.

Fixes: 3972ef6f830d ("tcg: Push merged memop+mmu_idx parameter to softmmu routines")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Leon Alrae <leon.alrae@imgtec.com>
Message-id: 1436433435-24898-2-git-send-email-james.hogan@imgtec.com
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Leon Alrae <leon.alrae@imgtec.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>