target/arm: arm_pamax() no longer needs to do feature propagation

target/arm: arm_pamax() no longer needs to do feature propagation

In arm_pamax(), we need to cope with the virt board calling this
function on a CPU object which has been inited but not realize.
We used to do propagation of feature-flag implications (such as
"V7VE implies LPAE") at realize, so we have some code in arm_pamax()
which manually checks for both V7VE and LPAE feature flags.

In commit b8f7959f28c4f36 we moved the feature propagation for
almost all features from realize to post-init. That means that
now when the virt board calls arm_pamax(), the feature propagation
has been done. So we can drop the manual propagation handling
and check only for the feature we actually care about, which
is ARM_FEATURE_LPAE.

Retain the comment that the virt board is calling this function
with a not completely realized CPU object, because that is a
potential beartrap for later changes which is worth calling out.

(Note that b8f7959f28c4f36 actually fixed a bug in the arm_pamax()
handling: arm_pamax() was missing a check for ARM_FEATURE_V8, so it
incorrectly thought that the qemu-system-arm 'max' CPU did not have
LPAE and turned off 'highmem' support in the virt board.  Following
b8f7959f28c4f36 qemu-system-arm 'max' is treated the same as
'cortex-a15' and other v7 LPAE CPUs, because the generic feature
propagation code does correctly propagate V8 -> V7VE -> LPAE.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240109143804.1118307-1-peter.maydell@linaro.org