target/arm: Replace TARGET_PAGE_ENTRY_EXTRA

target/arm: Replace TARGET_PAGE_ENTRY_EXTRA

TARGET_PAGE_ENTRY_EXTRA is a macro that allows guests to specify additional
fields for caching with the full TLB entry.  This macro is replaced with
a union in CPUTLBEntryFull, thus making CPUTLB target-agnostic at the
cost of slightly inflated CPUTLBEntryFull for non-arm guests.

Note, this is needed to ensure that fields in CPUTLB don't vary in
offset between various targets.

(arm is the only guest actually making use of this feature.)

Signed-off-by: Anton Johansson <anjo@rev.ng>
Message-Id: <20230912153428.17816-2-anjo@rev.ng>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>