iio: imu: bno055: serdev requires REGMAP

There are a ton of build errors when REGMAP is not set, so select
REGMAP to fix all of them.

Examples (not all of them):

../drivers/iio/imu/bno055/bno055_ser_core.c:495:15: error: variable 'bno055_ser_regmap_bus' has initializer but incomplete type
  495 | static struct regmap_bus bno055_ser_regmap_bus = {
../drivers/iio/imu/bno055/bno055_ser_core.c:496:10: error: 'struct regmap_bus' has no member named 'write'
  496 |         .write = bno055_ser_write_reg,
../drivers/iio/imu/bno055/bno055_ser_core.c:497:10: error: 'struct regmap_bus' has no member named 'read'
  497 |         .read = bno055_ser_read_reg,
../drivers/iio/imu/bno055/bno055_ser_core.c: In function 'bno055_ser_probe':
../drivers/iio/imu/bno055/bno055_ser_core.c:532:18: error: implicit declaration of function 'devm_regmap_init'; did you mean 'vmem_map_init'? [-Werror=implicit-function-declaration]
  532 |         regmap = devm_regmap_init(&serdev->dev, &bno055_ser_regmap_bus,
../drivers/iio/imu/bno055/bno055_ser_core.c:532:16: warning: assignment to 'struct regmap *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
  532 |         regmap = devm_regmap_init(&serdev->dev, &bno055_ser_regmap_bus,
../drivers/iio/imu/bno055/bno055_ser_core.c: At top level:
../drivers/iio/imu/bno055/bno055_ser_core.c:495:26: error: storage size of 'bno055_ser_regmap_bus' isn't known
  495 | static struct regmap_bus bno055_ser_regmap_bus = {

Fixes: 2eef5a9 ("iio: imu: add BNO055 serdev driver")
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Andrea Merello <[email protected]>
Cc: Jonathan Cameron <[email protected]>
Cc: Lars-Peter Clausen <[email protected]>
Cc: [email protected]
Cc: <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>

Author: rddunlap

drivers/iio/imu/bno055/Kconfig

@@ -8,6 +8,7 @@ config BOSCH_BNO055
 config BOSCH_BNO055_SERIAL
 	tristate "Bosch BNO055 attached via UART"
 	depends on SERIAL_DEV_BUS
+	select REGMAP
 	select BOSCH_BNO055
 	help
 	  Enable this to support Bosch BNO055 IMUs attached via UART.