Use round_up_overflow to avoid any integer overflow from
protocol count.
Thsi fixes below coverity issue -
CID 457880: (#1 of 1): Overflowed constant (INTEGER_OVERFLOW)
4. overflow_const: Expression count - 1U, where count is known
to be equal to 0, underflows the type of count - 1U, which is
type unsigned int.
Change-Id: Ib55599fcb2a522e57271a6a07fb9bfd07e6953b9
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>