i2c: lpi2c: add lpi2c driver for i.MX7ULP

Add lpi2c driver for i.MX7ULP.
Need to enable the two options to use this driver:
CONFIG_DM_I2C=y
CONFIG_SYS_I2C_IMX_LPI2C=y

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Acked-by: Heiko Schocher <hs@denx.de>
Cc: Stefano Babic <sbabic@denx.de>