driver: qspi: correct QSPI disable CS reset value

Correcting QSPI disable/unselect CS reset value.
CTRL_CORE_CONTROL_IO_2: QSPI_MEMMAPPED_CS[10:8]

This is not causing any issue, but its better
to untouch the reserved bits.

Praneeth Bajjuri <praneeth@ti.com>
Signed-off-by: Ravi Babu <ravibabu@ti.com>

drivers/spi/ti_qspi.c

@@ -45,7 +45,7 @@ DECLARE_GLOBAL_DATA_PTR;
 #define QSPI_XFER_DONE                  QSPI_WC
 #define MM_SWITCH                       0x01
 #define MEM_CS(cs)                      ((cs + 1) << 8)
-#define MEM_CS_UNSELECT                 0xfffff0ff
+#define MEM_CS_UNSELECT                 0xfffff8ff
 #define MMAP_START_ADDR_DRA		0x5c000000
 #define MMAP_START_ADDR_AM43x		0x30000000
 #define CORE_CTRL_IO                    0x4a002558