mfd: cpcap: Fix cpcap dmamask not set warnings

mfd: cpcap: Fix cpcap dmamask not set warnings

We have started to get a bunch of pointless dmamask not set warnings
that makes the output of dmesg -l err,warn hard to read with many
extra warnings:

cpcap-regulator cpcap-regulator.0: DMA mask not set
cpcap_adc cpcap_adc.0: DMA mask not set
cpcap_battery cpcap_battery.0: DMA mask not set
cpcap-charger cpcap-charger.0: DMA mask not set
cpcap-pwrbutton cpcap-pwrbutton.0: DMA mask not set
cpcap-led cpcap-led.0: DMA mask not set
cpcap-led cpcap-led.1: DMA mask not set
cpcap-led cpcap-led.2: DMA mask not set
cpcap-led cpcap-led.3: DMA mask not set
cpcap-led cpcap-led.4: DMA mask not set
cpcap-rtc cpcap-rtc.0: DMA mask not set
cpcap-usb-phy cpcap-usb-phy.0: DMA mask not set

This seems to have started with commit 4d8bde883bfb ("OF: Don't set
default coherent DMA mask"). We have the parent SPI controller use
DMA, while CPCAP driver and it's children do not. For audio, the
DMA is handled over I2S bus with the McBSP driver.

Cc: Carl Philipp Klemm <philipp@uvos.xyz>
Cc: Ivan Jelincic <parazyd@dyne.org>
Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Sicelo A. Mhlongo <absicsz@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>