ANDROID: arm64: add __va_function

With CFI, the compiler replaces function references with pointers
to the CFI jump table. This breaks passing these addresses to
code running at EL2, where the jump tables are not valid. Add a
__va_function macro similarly to the earlier __pa_function to take
address of the actual function in inline assembly and use that in
kvm_ksym_ref instead.

Bug: 163385976
Change-Id: I097b99409995512c00786300e7d18fe42c720a1b
(cherry picked from commit 2f4d6c9fd77c88ad0500aad4bf1f64aaf2654c49)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>