tcg: If DEBUG_TCGV, distinguish TCGv_ptr from TCGv_i32/TCGv_i64

tcg: If DEBUG_TCGV, distinguish TCGv_ptr from TCGv_i32/TCGv_i64

When compiling with DEBUG_TCGV enabled, make the TCGv_ptr type distinct
from TCGv_i32/TCGv_i64. This means that using an i32 or i64 TCG op to
manipulate a TCGv_ptr will always be detected at compile time, rather
than only if compiling on a host system with the other word size.

NB: the tcg_add_ptr and tcg_sub_ptr macros have been removed as they
were not used anywhere.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>