mtd: spi-nor: Fix write protection error with 1-byte length

mtd: spi-nor: Fix write protection error with 1-byte length

Incase of write operation at offset 0 and with data length 1, we are
observing write protection error.

sf write 0x400000 0 1
device 0 offset 0x0, size 0x1
offset 0x0 is protected and cannot be written
SF: 1 bytes @ 0x0 Written: ERROR -22

This is happening due to return of incorrect status of locked sectors
due to shifting of length in dual parallel connection.
Resolve this issue by avoiding data shift when data length is 1.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Acked-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>