FROMGIT: KVM: arm64: Mask response to FFA_FEATURE call

The minimum size and alignment boundary for FFA_RXTX_MAP is returned in
bit[1:0]. Mask off any other bits in w2 when reading the minimum buffer
size in hyp_ffa_post_init.

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Per Larsen <perlarsen@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

Bug: 280886201
(cherry picked from commit 3f595291
 https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git

 next)
Change-Id: I2e8234d1272d02f1f9c8b354f2c382445fa1a2c8
Signed-off-by: Per Larsen <perlarsen@google.com>