feat(fvp): increase MAX_XLAT_TABLES entries for DRTM support

DRTM implementation maps the DLME data region provided by the
DCE-preamble in BL31, hence increased MAX_XLAT_TABLES entries
count.

Signed-off-by: Manish V Badarkhe <manish.badarkhe@arm.com>
Signed-off-by: Lucian Paul-Trifu <lucian.paultrifu@gmail.com>
Change-Id: I5f0ac69e009c4f81d3590fdb1f4c0a7f73c5c99d

plat/arm/board/fvp/include/platform_def.h

@@ -144,6 +144,8 @@
 #  else
 #   if ENABLE_RME
 #    define MAX_XLAT_TABLES		8
+#   elif DRTM_SUPPORT
+#    define MAX_XLAT_TABLES		8
 #   else
 #    define MAX_XLAT_TABLES		7
 #   endif