KVM: arm64: pkvm: Drop unnecessary FP/SIMD trap handler

The pVM-specific FP/SIMD trap handler just calls straight into the
generic trap handler. Avoid the indirection and just call the hyp
handler directly.

Note that the BUILD_BUG_ON() pattern is repeated in
pvm_init_traps_aa64pfr0(), which is likely a better home for it.

No functional change intended.

Signed-off-by: Oliver Upton <oupton@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220509162559.2387784-2-oupton@google.com