MdePkg/PiFirmwareFile: express IS_SECTION2 in terms of SECTION_SIZE

MdePkg/PiFirmwareFile: express IS_SECTION2 in terms of SECTION_SIZE

The IS_SECTION2() function-like macro duplicates the SECTION_SIZE()
calculation, just to compare the computed size against 0xFFFFFF. Invoke
SECTION_SIZE() instead; only preserve the comparison.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1710
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>