mtd: spi-nor: Only set Micron quad-read mode when controller in 4-lane TX mode

Micron QUAD mode expects command, address and data on 4 lanes instead of just
one for command (extended SPI mode). This requires the controller to be in a
special mode, so check first if the controller could be in that mode. If a
controller does not have the SPI_TX_QUAD mode set, this setting has no chance
of being valid at all, so don't try to enable it then, and just keep using
the extended SPI mode.

Tested on a Zynq 7000 with a n25q256a flash chip, this failed to function
because of the introduction of:
"driver:mtd:spi-nor: Add quad I/O support for Micron spi nor"
This commit sets QUAD mode for most Micron chips without asking the controller
whether it's possible to do so, and without telling the controller that a
different mode is required, so it couldn't work.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Acked-by: Harini Katakam <harinik@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>