drivers: flash: spi_nor.c: Correct the calculation of SECTORS_COUNT

The patch 44758977f81bb61d4f299ade72ff82517c11af7a made a change where
SECTORS_COUNT was not calculated properly. This patch corrects it.

Signed-off-by: Rajavardhan Gundi <rajavardhan.gundi@intel.com>
1 file changed