target/arm: Replace MTEDESC ESIZE+TSIZE with SIZEM1

target/arm: Replace MTEDESC ESIZE+TSIZE with SIZEM1

After recent changes, mte_checkN does not use ESIZE,
and mte_check1 never used TSIZE.  We can combine the
two into a single field: SIZEM1.

Choose to pass size - 1 because size == 0 is never used,
our immediate need in mte_probe_int is for the address
of the last byte (ptr + size - 1), and since almost all
operations are powers of 2, this makes the immediate
constant one bit smaller.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210416183106.1516563-6-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>