lib: utils/ipi: Fix size check in aclint_mswi_cold_init()

Currently, the ACLINT MSWI size check is forcing size to be at least
0x4000. This is inappropriate check because most systems will never
utilize full 16KB for a single ACLINT MSWI device so instead we should
check that ACLINT MSWI size is enough for on the associated HARTs.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Dong Du <Dd_nirvana@sjtu.edu.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>