i2c: Remove unncessary HAS_I2C_DW Kconfig symbol

The HAS_I2C_DW was to limit Kconfig visibility to only platforms
that utilize the I2C DW IP.  The Kconfig for I2C_DW depends on
DT_HAS_SNPS_DESIGNWARE_I2C_ENABLED which will cause the same
visbility limitation to only platforms that have I2C DW devicetree
nodes.  Thus we can remove HAS_I2C_DW and its references.

Signed-off-by: Kumar Gala <galak@kernel.org>