Platform/ARM/N1Sdp: manually poll QSPI status bit after erase/write

This patch adds a function to poll Nor flash memory's status register
bit (WIP bit) to wait for an erase/write operation to complete.
The polling timeout is set to 1 second.

Signed-off-by: sahil <sahil@arm.com>
Change-Id: Ie678b7586671964ae0f8506a0542d73cbddddfe4