spi: ti_qspi: Add delay for successful bulk erase.

Bulk erase is not happening properly on dra7 due to erase timing constraints,
add a delay so that erase timing constraints are properly met.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Tested-by: Yebio Mesfin <ymesfin@ti.com>

drivers/spi/ti_qspi.c

@@ -314,6 +314,9 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 			qslave->cmd |= QSPI_RD_SNGL;
 			debug("rx cmd %08x dc %08x\n",
 			      qslave->cmd, qslave->dc);
+			#ifdef CONFIG_DRA7XX
+				udelay(500);
+			#endif
 			writel(qslave->cmd, &qslave->base->cmd);
 			status = readl(&qslave->base->status);
 			timeout = QSPI_TIMEOUT;