chore(app/random): fix integer overflow issue reported by Coverity

Fix potential integer overflow error reported by Coverity.
This patch eliminates the problematic typecast from

    ret = (unsigned long)prng_init(arg_0);

Signed-off-by: Mate Toth-Pal <mate.toth-pal@arm.com>
Change-Id: Ibef4eaa1cb5f7ca7987373eee4a6648ebe4d80a8
1 file changed