drivers: i2c: rename IRQ SHARED/DIRECT Kconfig options

I2C_SHARED_IRQ, I2C_0_IRQ_SHARED, I2C_0_IRQ_DIRECT Kconfig options
are DW driver specific. Its presence is confusing for a user of any
other I2C driver than DW. This patch renames these options to include
DW string and makes it visible only for DW I2C driver. This is a
similar implementation to that used by ETH DW Ethernet driver.

Change-Id: I795506f9b103c028a22317df9ad632dce5cd1343
Signed-off-by: Piotr Mienkowski <piotr.mienkowski@gmail.com>