drivers: spi: Fix data loss issue in QSPI

drivers: spi: Fix data loss issue in QSPI

QSPI driver performs chip select operation before every read/write
access. During this operation, driver needs to enable and disable
the QSPI controller. This may cause data loss if there is inadvertent
halting of any ongoing read/write operation. To avoid this scenario,
waiting for the QSPI status to be idle before next read/write
operation is implemented.

Signed-off-by: Naresh Kumar Ravulapalli <nareshkumar.ravulapalli@altera.com>
Reviewed-by: Tien Fong Chee <tien.fong.chee@intel.com>