x86/S3: Drop {save,restore}_rest_processor_state() completely

x86/S3: Drop {save,restore}_rest_processor_state() completely

There is no need to save/restore FS/GS/XCR0 state.  It will be handled
suitably on the context switch away from the idle.

The CR4 restoration in restore_rest_processor_state() was actually fighting
later code in enter_state() which tried to keep CR4.MCE clear until everything
was set up.  Delete the intermediate restoration, and defer final restoration
until after MCE is reconfigured.

Restoring PAT can be done earlier, and ideally before paging is enabled.  By
moving it into the trampoline during the setup for 64bit, the call can be
dropped from cpu_init().  The EFI path boot path doesn't disable paging, so
make the adjustment when switching onto Xen's pagetables.

The only remaing piece of restoration is load_system_tables(), so suspend.c
can be deleted in its entirety.

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