x86/hvm: Rework nested hap functions to reduce parameters

x86/hvm: Rework nested hap functions to reduce parameters

Most functions in this call chain have 8 parameters, meaning that the final
two booleans are spilled to the stack for calls.

First, delete nestedhap_walk_L1_p2m and introduce nhvm_hap_walk_L1_p2m() as a
thin wrapper around hvm_funcs, just like all the other nhvm_*() hooks.  This
involves including xen/mm.h as the forward declaration of struct npfec is no
longer enough.

Next, replace the triple of booleans with struct npfec, which contains the
same information in the bottom 3 bits.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>