x86/pagewalk: Improve print_gw()

x86/pagewalk: Improve print_gw()

print_gw() has no callers, meaning that it only gets used as part of manual
debugging.  As such, the FILE/LINE references are of no practical use, and
voluminous in the log.  Additionally, the function becoming empty in a
non-debug build is unhelpful.  Switch from gdprintk() to gprintk().

Print the entry and mfn for a specific level on the same line.  This halves
the number of lines printed overall.  There needs to be a small adjustment to
the #ifdef'ary to maintain the proper l3e behaviour for 3-level paging, where
there is no l3mfn to print.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>