x86-64/physdevop: reduce generated code duplication

x86-64/physdevop: reduce generated code duplication

At least all the helper functions can be used by both the native and
the compat-mode implementations, requiring their parameters to be
adjusted.

Additionally, rather than having the compat mode wrapper source file
blindly define the native structures to be replaced by the compat mode
ones, replace unnecessary (un-)definitions by layout match checks.

In a second step, do_physdev_op() could be split into a part that
needs
re-compilation for compat mode handling and one that can be used for
native and compat mode.

Signed-off-by: Jan Beulich <jbeulich@novell.com>