scmi: fix psci protocol-count assertions

Created by: HelloGravity

I got assertion errors when trying to work with mod_scmi with a PSCI agent with protocol_count=0.

It turned out the assertion itself has a bug, it does not allow scmi_ctx.protocol_count to be equal to scmi_ctx.config->dis_protocol_count_psci.

The reason for the assertion is so that the subtraction scmi_ctx.protocol_count - scmi_ctx.config->dis_protocol_count_psci would not be negative. But no reason it cannot be 0.

It worked after fixing these 2 assertions.