tests: intel_s1000: Fix the spi flash tests for R/W
tests: intel_s1000: Fix the spi flash tests for R/W

The tests are modified to reflect the changed return values
the spi flash read and write APIs return.

Signed-off-by: Rajavardhan Gundi <b08addc5b57f0413e0a4ff6bc495295037640485@intel.com>

finikorg/zephyr,galak/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,explora26/zephyr,nashif/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,explora26/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,nashif/zephyr,punitvara/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,punitvara/zephyr,Vudentz/zephyr,Vudentz/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,ldts/zephyr,finikorg/zephyr,ldts/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,nashif/zephyr,punitvara/zephyr