Fix RiscV support - Rendering issue for armv7l

Fix RiscV support - Rendering issue for armv7l

Commit fixes change introduced in RiscV support for M120.

On armv7l (built with ./tizen_src/build/build_standard_armv7l) the
lack of specialized template of SerializedSizeSimple() for size_t
caused rendering issue and usage of illegal instruction when
running chromium-efl for armv7l.

Specialization was originally commented out due to compliation error caused
by gcc bug that does not allow declaration of specialized template
outside of the namespace.

Now the specialization is introduced in template where it will
return appropriate value depending on the type of typename T

Change-Id: If713bd0c0d6c1a0ed91cc2f627c314a20471ceb7
Signed-off-by: Aleksander Świniarski <a.swiniarski@samsung.com>