target/arm: Always apply CNTVOFF_EL2 for CNTV_TVAL_EL02 accesses

target/arm: Always apply CNTVOFF_EL2 for CNTV_TVAL_EL02 accesses

Currently we handle CNTV_TVAL_EL02 by calling gt_tval_read() for the
EL1 virt timer.  This is almost correct, but the underlying
CNTV_TVAL_EL0 register behaves slightly differently.  CNTV_TVAL_EL02
always applies the CNTVOFF_EL2 offset; CNTV_TVAL_EL0 doesn't do so if
we're at EL2 and HCR_EL2.E2H is 1.

We were getting this wrong, because we ended up in
gt_virt_cnt_offset() and did the E2H check.

Factor out the tval read/write calculation from the selection of the
offset, so that we can special case gt_virt_tval_read() and
gt_virt_tval_write() to unconditionally pass CNTVOFF_EL2.

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20250204125009.2281315-5-peter.maydell@linaro.org
(cherry picked from commit 4aecd4b442d7abb4355896d878ffc9b028625b01)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>