BACKPORT: FROMLIST: virt: gunyah: Add hypercalls to identify Gunyah

Add hypercalls to identify when Linux is running in a virtual machine
under Gunyah.

There are two calls to help identify Gunyah:

1. gh_hypercall_get_uid() returns a UID when running under a Gunyah
   hypervisor.
2. gh_hypercall_hyp_identify() returns build information and a set of
   feature flags that are supported by Gunyah.

Bug: 338347082
Link: https://lore.kernel.org/all/20240222-gunyah-v17-4-1e9da6763d38@quicinc.com/


Change-Id: I272957ef883fde18db67c5130750190a33ec3f13
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
Signed-off-by: Sreenad Menon <quic_sreemeno@quicinc.com>