x86/dom0: fix restoring %cr3 and the mapcache override on PV build error

x86/dom0: fix restoring %cr3 and the mapcache override on PV build error

One of the error paths in the PV dom0 builder section that runs on the guest
page-tables wasn't restoring the Xen value of %cr3, neither removing the
mapcache override.

Fixes: 079ff2d32c3d ('libelf-loader: introduce elf_load_image')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: 1fc3f77113dd43b14fa7ef5936dcdba120c0b63f
master date: 2024-07-31 12:41:02 +0200