x86/mm: Drop MEM_LOG() and correct some printed information

x86/mm: Drop MEM_LOG() and correct some printed information

MEM_LOG() is just a thin wrapper around gdprintk(), obscuring some of the
common information.  Inline it, and take the opportunity to correct some of
the printked information.

Some corrections, each where appropriate:
 * Correction of pfn/mfn terms and consistent use of PRI_pfn/mfn
 * s!I/O!MMIO!
 * Consistently represent domains using d%d notation
 * Use 0x prefix for otherwise unqualified hex numbers
 * Remove "ptwr_emulate:" prefix, as the embedded __func__ is already clear
 * Provide more useful slot information
 * Delete some not-very-helpful lines entirely

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Release-acked-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>