mfd: arizona: Rename thermal shutdown interrupt

Newer versions of the IP introduce short circuit protection which will
also shutdown the speaker. Rename the interrupt and associated register
bits associated with thermal events to better fit the function and avoid
conflict with future interrupt additions.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>