fix(plat/st): correct signedness comparison issue
fix(plat/st): correct signedness comparison issue

Add casts where required to avoid compialtion error when enabling
-Wsign-compare in shared resources file.
The assert is also corrected to match the correct range (change ||
to &&).

Change-Id: Ie4c9c0c935d39ff9a2165b909172aacb3e94ab4d
Signed-off-by: Yann Gautier <e753f6969c288905606e3c07464886d4f1fc1be0@st.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware