cmd: eeprom: add bus switching support for all i2c drivers

The i2c_init function is always provided when CONFIG_SYS_I2C is
defined. No need to limit ourselves to just one supported I2C driver
(soft_i2c). Update the #ifdef conditions to support bus switching for
all I2C drivers.

Cc: Heiko Schocher <hs@denx.de>
Cc: Marek Vasut <marex@denx.de>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Cc: Tom Rini <trini@konsulko.com>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>