x86/HVM: patch indirect calls through hvm_funcs to direct ones

x86/HVM: patch indirect calls through hvm_funcs to direct ones

This is intentionally not touching hooks used rarely (or not at all)
during the lifetime of a VM, like {domain,vcpu}_initialise or cpu_up,
as well as nested, VM event, and altp2m ones (they can all be done
later, if so desired). Virtual Interrupt delivery ones will be dealt
with in a subsequent patch.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>