lib: utils/ipi: buffer overrun aclint_mswi_cold_init

The parameter checks in aclint_mswi_cold_init() don't guard against a
buffer overrun.

mswi_hartid2data is defined as an array of SBI_HARTMASK_MAX_BITS entries.
The current check allows

    mswi->hart_count = ACLINT_MSWI_MAX_HARTS
    mswi->first_hartid = SBI_HARTMASK_MAX_BITS - 1.

With these values mswi_hartid2data will be accessed at index

    SBI_HARTMASK_MAX_BITS + SBI_HARTMASK_MAX_BITS - 2.

We have to check the sum of mswi->first_hartid and mswi->hart_count.

Furthermore mswi->hart_count = 0 would not make much sense.

Addresses-Coverity-ID: 1529705 ("Out-of-bounds write")
Fixes: 5a049fe1

 ("lib: utils/ipi: Add ACLINT MSWI library")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>