ANDROID: KVM: arm64: Copy pvmfw into guest pages during donation from the host

When the host donates a page to a protected guest at an IPA which
coincides with the PVM firmware load address, copy-in the relevant
firmware page after unmapping it from the host but before mapping it
into the guest.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 254819795
Change-Id: I8cec813fa52938945f3122655deb785523a96ec8
Signed-off-by: Quentin Perret <qperret@google.com>