ARM: OMAP2+: UART: Move errata handling from serial.c to omap-serial

Move the errata handling mechanism from serial.c to omap-serial file
and utilise the same func in driver file.

Errata i202, i291 are moved to be handled with omap-serial
Moving the errata macro from serial.c file to driver header file
as from on errata will be handled in driver file itself.
Corrected errata id from chapter reference 2.15 to errata id i291.

Removed errata and dma_enabled fields from omap_uart_state struct
as they are no more needed with errata handling done within omap-serial.

Signed-off-by: Govindraj.R <govindraj.raja@ti.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Kevin Hilman <khilman@ti.com>