firmware: arm_scmi: fix bitfield definitions for SENSOR_DESC attributes

As per the SCMI specification the bitfields for SENSOR_DESC attributes
are as follows:
attributes_low 	[7:0] 	Number of trip points supported
attributes_high	[15:11]	The power-of-10 multiplier in 2's-complement
			format that is applied to the sensor units

Looks like the code developed during the draft versions of the
specification slipped through and are wrong with respect to final
released version. Fix them by adjusting the bitfields appropriately.

Fixes: 5179c523 ("firmware: arm_scmi: add initial support for sensor protocol")
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>