EFI: drop copy-in from QueryVariableInfo()'s OUT-only variable bouncing

EFI: drop copy-in from QueryVariableInfo()'s OUT-only variable bouncing

While be12fcca8b78 ("efi: fix alignment of function parameters in compat
mode") intentionally bounced them both ways to avoid any functional
change so close to the release of 4.16, the bouncing-in shouldn't really
be needed. In exchange the local variables need to gain initializers to
avoid copying back prior stack contents.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>