i2c, mpc83xx: add CONFIG_SYS_I2C_INIT_BOARD for fsl_i2c

This patch adds the possibility to call a board specific
i2c bus reset routine for the fsl_i2c bus driver, and adds
this option for the keymile kmeter1 board.

The deblock sequence for this board is implemented and
tested in the following way:

CR = 0x20 (release SDA and SCL pin)
CR = 0xa0 (start read)
dummy read
dummy read
if 2. dummy read == 0x00
	3. dummy read

CR = 0x80 (SDA and SCL now 1 SR = 0x86)
CR = 0x00 (Modul reset SR=0x81)
CR = 0x80 (SDA and SCL = 1, SR = 0x81)

Signed-off-by: Heiko Schocher <hs@denx.de>