tcg: Remove redundant pointer from TCGContext

The pointer entry 'temps' always refers to the array entry 'static_temps'.
Removing the pointer and renaming 'static_temps' to 'temps' reduces the
size of TCGContext (4 or 8 byte) and allows better code generation.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>