KVM: arm64: Fix some documentation build warnings

As warned with make htmldocs:

	.../Documentation/virt/kvm/devices/vcpu.rst:70: WARNING: Malformed table.
	Text in column margin in table line 2.

	=======  ======================================================
	-ENODEV: PMUv3 not supported or GIC not initialized
	-ENXIO:  PMUv3 not properly configured or in-kernel irqchip not
	         configured as required prior to calling this attribute
	-EBUSY:  PMUv3 already initialized
	-EINVAL: Invalid filter range
	=======  ======================================================

The ':' character for two lines are above the size of the column.
Besides that, other tables at the file doesn't use ':', so
just drop them.

While here, also fix this warning also introduced at the same patch:

	.../Documentation/virt/kvm/devices/vcpu.rst:88: WARNING: Block quote ends without a blank line; unexpected unindent.

By marking the C code as a literal block.

Fixes: 8be86a5e ("KVM: arm64: Document PMU filtering API")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/b5385dd0213f1f070667925bf7a807bf5270ba78.1601616399.git.mchehab+huawei@kernel.org