sf: fix support of QSPI memories and controllers

Hi all,

This series of patches fixes and extend the support of QSPI memories in the SPI flash framework. The updates are split into many parts to make it easier to understand and review but they should be considered as a whole.

This was tested on a Atmel sama5d2 xplained board with a Micron n25q128a memory.

Best regards,

Cyrille

Cyrille Pitchen (18):
Revert "sf: Fix quad bit set for micron devices"
sf: call spi_claim_bus() and spi_release_bus() only once per read,
write or erase
sf: replace spi_flash_read_common() calls by spi_flash_cmd_read()
sf: remove spi_flash_write_common()
sf: export spi_flash_wait_ready() function
sf: share erase generic algorithm
sf: share write generic algorithm
sf: share read generic algorithm
sf: add hooks to handle register read and write operations
sf: move support of SST flash into generic spi_flash_write_alg()

sf: fix selection of supported READ commands for QSPI memories
sf: fix detection of QSPI memories when they boot in Quad or Dual mode
sf: add helper function to set the number of dummy bytes
sf: add 4byte address opcodes
sf: prepare next fixes to support of QSPI memories by manufacturer
sf: fix support of Micron memories
ARM: at91: clock: add function to get QSPI clocks
sf: add driver for Atmel QSPI controller