i2c: bfin-twi: move bits macros and structs in header from arch include to generic include

The ADI TWI peripheral is not binding to the Blackfin processor only.
The bits macros and structs should be put in the generic include header.
And update head file path in drivers accordingly.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>