Revert "ANDROID: pkvm: x86: Add pkvm guest virtualization exception (#VE)"

This reverts commit 2bd8ee5b.

pKVM guests don't use #VE anymore, and the up-to-date pKVM-IA hypervisor
code does not even include an implementation of the PKVM_GHC_GET_VE_INFO
hypercall. So remove its support from the guest kernel.

The actual motivation for this cleanup is to free up the hypercall
number used by the deprecated PKVM_GHC_GET_VE_INFO to use it for the
upcoming new hypercall for starting secondary CPUs.

Note that this not 100% revert: mmio_write()/mmio_read() which were
introduced by the original commit are not removed, since now they are
reused for PV MMIO accessors pkvm_mmio_*() which were introduced later
(and which replaced the original #VE based solution).

Bug: 374338925
Test: run various VMs
Upstream-Task: 402758258

Change-Id: Id54f2f07428edd11d185b9456c024e0052a631c4
Signed-off-by: Dmytro Maluka <dmaluka@google.com>