libxc: remove stale error check for domain size in xc_sr_save_x86_hvm.c
Long ago domains to be saved were limited to 1TB size due to the
migration stream v1 limitations which used a 32 bit value for the
PFN and the frame type (4 bits) leaving only 28 bits for the PFN.
Migration stream V2 uses a 64 bit value for this purpose, so there
is no need to refuse saving (or migrating) domains larger than 1 TB.
For 32 bit toolstacks there is still a size limit, as domains larger
than about 1TB will lead to an exhausted virtual address space of the
saving process. So keep the test for 32 bit, but don't base it on the
page type macros. As a migration could lead to the situation where a
32 bit toolstack would have to handle such a large domain (in case the
sending side is 64 bit) the same test should be added for restoring a