OvmfPkg/XenPvBlkDxe: Don't include system inttypes.h

EDK II code should not include system include files.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/OvmfPkg@16341 6f19259b-4bc3-4df7-8a09-765794883524