ANDROID: KVM: arm64: Allow tweaking HCR_EL2 from modules

pKVM modules may need to enable additional traps on top of what pKVM
already enables. To allow this use-case, expose a function allowing to
manipulate HCR_EL2 on the current CPU. This configuration will be
persistent across power management cycles and such as it is propagated
all the way to the init params per-cpu struct.

Bug: 245034629
Change-Id: I21d596bd1d01f4edc48a188cc3c2eb78dc9a4444
Signed-off-by: Quentin Perret <qperret@google.com>