Input: cap11xx - cache hardware ID registers

The cap11xx devices have three hardware identification registers which are
currently marked as volatile, preventing caching of those registers. This
is not ideal since the registers should never change at runtime, we should
be able to cache the value after the first read. Stop marking the registers
as volatile, we don't have register defaults specified in the driver so
this will result in reading from the hardware on first use.

Signed-off-by: Mark Brown <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/keyboard/cap11xx.c

···
 	case CAP11XX_REG_SENOR_DELTA(3):
 	case CAP11XX_REG_SENOR_DELTA(4):
 	case CAP11XX_REG_SENOR_DELTA(5):
-	case CAP11XX_REG_PRODUCT_ID:
-	case CAP11XX_REG_MANUFACTURER_ID:
-	case CAP11XX_REG_REVISION:
 		return true;
 	}