firmware: arm_scmi: Fix frequency truncation by promoting multiplier type

firmware: arm_scmi: Fix frequency truncation by promoting multiplier type

Fix the possible frequency truncation for all values equal to or greater
4GHz on 64bit machines by updating the multiplier 'mult_factor' to
'unsigned long' type. It is also possible that the multiplier itself can
be greater than or equal to 2^32. So we need to also fix the equation
computing the value of the multiplier.

Fixes: a9e3fbfaa0ff ("firmware: arm_scmi: add initial support for performance protocol")
Reported-by: Sibi Sankar <quic_sibis@quicinc.com>
Closes: https://lore.kernel.org/all/20231129065748.19871-3-quic_sibis@quicinc.com/
Cc: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20231130204343.503076-1-sudeep.holla@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>