staging:iio:mxs-lradc Fix large integer implicitly truncated to unsigned warning

staging:iio:mxs-lradc Fix large integer implicitly truncated to unsigned warning

The change to using BIT(20) for one of the bit shifts resulted
in a constant becoming unsigned. When combined with the existing
signed constants in a couple of places, this caused possible trouble,
hence the warnings:

drivers/staging/iio/adc/mxs-lradc.c: In function ‘mxs_lradc_complete_touch_event’:
drivers/staging/iio/adc/mxs-lradc.c:325:5: warning: large integer implicitly truncated to unsigned type [-Woverflow]
     (((x) << LRADC_DELAY_TRIGGER_LRADCS_OFFSET) & \
     ^
drivers/staging/iio/adc/mxs-lradc.c:734:7: note: in expansion of macro ‘LRADC_DELAY_TRIGGER’
       LRADC_DELAY_TRIGGER(1 << TOUCHSCREEN_VCHANNEL1) |
       ^
  LD [M]  drivers/staging/iio/accel/adis16201.o
drivers/staging/iio/adc/mxs-lradc.c: In function ‘mxs_lradc_buffer_preenable’:
drivers/staging/iio/adc/mxs-lradc.c:322:42: warning: large integer implicitly truncated to unsigned type [-Woverflow]
 #define LRADC_DELAY_TRIGGER_LRADCS_MASK  (0xff << 24)
                                          ^
drivers/staging/iio/adc/mxs-lradc.c:1308:29: note: in expansion of macro ‘LRADC_DELAY_TRIGGER_LRADCS_MASK’
  mxs_lradc_reg_clear(lradc, LRADC_DELAY_TRIGGER_LRADCS_MASK |
                             ^
drivers/staging/iio/adc/mxs-lradc.c: In function ‘mxs_lradc_buffer_postdisable’:
drivers/staging/iio/adc/mxs-lradc.c:322:42: warning: large integer implicitly truncated to unsigned type [-Woverflow]
 #define LRADC_DELAY_TRIGGER_LRADCS_MASK  (0xff << 24)
                                          ^
drivers/staging/iio/adc/mxs-lradc.c:1327:29: note: in expansion of macro ‘LRADC_DELAY_TRIGGER_LRADCS_MASK’
  mxs_lradc_reg_clear(lradc, LRADC_DELAY_TRIGGER_LRADCS_MASK |

The simplest fix is to force LRADC_DELAY_TRIGGER_LRADCS_MASK to be
a shift of an unsigned 0xff rather than a signed one.

This is ugly considering it is the only constant in the driver which
is so forced, but it does deal with the issue.

Fixes: e0c961bdaf27 (iio: adc: mxs-lradc: Prefer using the BIT macro)
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>