spi: fsl_qspi: Pet watchdog even more

Pet the watchdog once upon each command call (qspi_xfer) and during
each loop iteration in several commands.

This fixes a watchdog reset especially during erase command.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Reviewed-by: York Sun <york.sun@nxp.com>