tcg: Split rem requirement from div requirement

There are several hosts with only a "div" insn.  Remainder is computed
manually from the quotient and inputs.  We can do this generically.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/tcg/mips/tcg-target.h b/tcg/mips/tcg-target.h
index 6155327..a438950 100644
--- a/tcg/mips/tcg-target.h
+++ b/tcg/mips/tcg-target.h
@@ -79,6 +79,7 @@
 
 /* optional instructions */
 #define TCG_TARGET_HAS_div_i32          1
+#define TCG_TARGET_HAS_rem_i32          1
 #define TCG_TARGET_HAS_not_i32          1
 #define TCG_TARGET_HAS_nor_i32          1
 #define TCG_TARGET_HAS_ext8s_i32        1