designware_i2c: disable i2c controller during target address setup

As it is stated in DesignWare I2C databook: writes to IC_TAR (0x4)
register succeed only when IC_ENABLE[0] is set to 0.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Tom Rini <trini@ti.com>
cc: Armando Visconti <armando.visconti@st.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Heiko Schocher <hs@denx.de>
Cc: Vipin KUMAR <vipin.kumar@st.com>
Cc: Tom Rix <Tom.Rix@windriver.com>
Cc: Mischa Jonker <mjonker@synopsys.com>
designware_i2c: remove 10msec delay in i2c_xfer_finish

This delay applies to any data transfer on I2C bus.

For example 1kB data read with per-byte access (which happens if
environment is stored in I2C EEPROM) takes more than 10 seconds.

Moreover data bus driver has to care about bus state and data transfer,
but not about internal states of attached devices.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Tom Rini <trini@ti.com>
cc: Armando Visconti <armando.visconti@st.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Heiko Schocher <hs@denx.de>
Cc: Vipin KUMAR <vipin.kumar@st.com>
Cc: Tom Rix <Tom.Rix@windriver.com>
Cc: Mischa Jonker <mjonker@synopsys.com>
cmd_eeprom: fix i2c_{read|write} usage if env is in I2C EEPROM

Data "offset" is not used directly in case of I2C EEPROM. Istead it is
split into "block number" and "offset within mentioned block". Which are
"addr[0]" and "addr[1]" respectively.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
cc: Peter Tyser <ptyser@xes-inc.com>
Cc: Heiko Schocher <hs@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Mischa Jonker <mjonker@synopsys.com>
ARC: add support of I2C EEPROM

Also we store environment in this EEPROM now while NAND is not fixed.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>