regulator: pfuze100: REGULATOR_PFUZE100 needs to select REGMAP_I2C

This fixes below build errors:

  CC [M]  drivers/regulator/pfuze100-regulator.o
drivers/regulator/pfuze100-regulator.c:342:21: error: variable 'pfuze_regmap_config' has initializer but incomplete type
drivers/regulator/pfuze100-regulator.c:343:2: error: unknown field 'reg_bits' specified in initializer
drivers/regulator/pfuze100-regulator.c:343:2: warning: excess elements in struct initializer [enabled by default]
drivers/regulator/pfuze100-regulator.c:343:2: warning: (near initialization for 'pfuze_regmap_config') [enabled by default]
drivers/regulator/pfuze100-regulator.c:344:2: error: unknown field 'val_bits' specified in initializer
drivers/regulator/pfuze100-regulator.c:344:2: warning: excess elements in struct initializer [enabled by default]
drivers/regulator/pfuze100-regulator.c:344:2: warning: (near initialization for 'pfuze_regmap_config') [enabled by default]
drivers/regulator/pfuze100-regulator.c:345:2: error: unknown field 'max_register' specified in initializer
drivers/regulator/pfuze100-regulator.c:345:2: warning: excess elements in struct initializer [enabled by default]
drivers/regulator/pfuze100-regulator.c:345:2: warning: (near initialization for 'pfuze_regmap_config') [enabled by default]
drivers/regulator/pfuze100-regulator.c:346:2: error: unknown field 'cache_type' specified in initializer
drivers/regulator/pfuze100-regulator.c:346:2: warning: excess elements in struct initializer [enabled by default]
drivers/regulator/pfuze100-regulator.c:346:2: warning: (near initialization for 'pfuze_regmap_config') [enabled by default]
drivers/regulator/pfuze100-regulator.c: In function 'pfuze100_regulator_probe':
drivers/regulator/pfuze100-regulator.c:370:2: error: implicit declaration of function 'devm_regmap_init_i2c' [-Werror=implicit-function-declaration]
drivers/regulator/pfuze100-regulator.c:370:21: warning: assignment makes pointer from integer without a cast [enabled by default]
cc1: some warnings being treated as errors
make[2]: *** [drivers/regulator/pfuze100-regulator.o] Error 1
make[1]: *** [drivers/regulator] Error 2
make: *** [drivers] Error 2

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@linaro.org>