tcg-mips: Split out tcg_out_call

Signed-off-by: Richard Henderson <rth@twiddle.net>
tci: Create tcg_out_call

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Make call address a constant parameter

Avoid allocating a tcg temporary to hold the constant address,
and instead place it directly into the op_call arguments.

At the same time, convert to the newly introduced tcg_out_call
backend function, rather than invoking tcg_out_op for the call.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg: Remove unreachable code in tcg_out_op and op_defs

The INDEX_op_call case has just been obsoleted; the mov and movi
cases have not been reachable for years.  Attempt to document this
both in each tcg_out_op switch, and via TCG_OPF_NOT_PRESENT.

Because of the TCG_OPF_NOT_PRESENT change, this must be done for
all targets in a single commit.

Signed-off-by: Richard Henderson <rth@twiddle.net>