firmware: arm_scmi: Do not use !! on boolean when setting msg->flags

firmware: arm_scmi: Do not use !! on boolean when setting msg->flags

Both pc->async_powercap_cap_set and ignore_dresp are already boolean.
Use of !! on them is obviously dubious.

Sparse reports:
drivers/firmware/arm_scmi/powercap.c:363:17: warning: dubious: x & !y
drivers/firmware/arm_scmi/powercap.c:363:17: warning: dubious: x & !y

Remove the unnecessary !! and get rid of the warning.

Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20230921085257.3125744-1-sudeep.holla@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>