spi: atmel-quadspi: Avoid overwriting MR register settings

Port these commits:

- v6.11-rc5-90-g329ca3eed4a9a ("spi: atmel-quadspi: Avoid overwriting delay register settings")
- v6.12-rc1-1-g162d9b5d2308c ("spi: atmel-quadspi: Fix wrong register value written to MR").
- v6.13-rc2-27-gf663898d047a7 ("spi: atmel-quadspi: Factor out switching to Serial Memory Mode to function")

Cc: Csókás Bence <csokas.bence@prolan.hu>
Signed-off-by: Alexander Dahl <ada@thorsis.com>
1 file changed