boards: frdm_k22f: Add support for frdm_stbc_agm01

Provide the arduino_i2c node name from i2c_0.
Provide pinmux for frdm_stbc_agm01.

The frdm_stbc_agm01 supplies access to an FXOS8700 and FXAS21002.
when using frdm_stbc_agm01 with frdm_k22f, the FXAS21002 sample
sensor project can be utilized and the FXOS8700 sample sensor
project utilizes the shield's FXOS8700.

Signed-off-by: Ryan Holleran <rhollerar@gmail.com>