firmware: arm_scmi: Fix wrong fastchannel initialization

Fastchannels are initialized with an incorrect index(POWERCAP_PAI_GET) in:
commit 2441caa8 ("firmware: arm_scmi: Populate fast channel rate_limit")

Fix this and provide a correct index(POWERCAP_FC_PAI)

Fixes: 2441caa8 ("firmware: arm_scmi: Populate fast channel rate_limit")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202403100744.7Op3PI8L-lkp@intel.com/


Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Link: https://lore.kernel.org/r/20240311090413.1710725-1-pierre.gondois@arm.com


Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>