spi: designware_spi: Some fixes / changes

spi: designware_spi: Some fixes / changes

As suggested by Pavel, here some fixes to the designware SPI driver:

- Spelling fixes
- Comment for timeout added
- Removed n_bytes completely (bits_per_word is enough for this)
- Unput clock now not defined via macro. The function to
  get the clock value is now called directly from within the driver

Signed-off-by: Stefan Roese <[email protected]>
Cc: Chin Liang See <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Vince Bridgers <[email protected]>
Cc: Marek Vasut <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Cc: Jagannadha Sutradharudu Teki <[email protected]>