[IA64] Format /proc/pal/*/version_info correctly

/proc/pal/*/version_info is a bit confusing.  HP firmware, at least,
reports 07.31 instead of 0.7.31.  Also, the comment is out of place;
it's an internal detail about the implementation of ia64_pal_version.
Since the 2.2 revision of the SDM still states that PAL_VERSION can
be called in virtual mode, correct the comment to be more accurate.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Tony Luck <tony.luck@intel.com>