tests: drivers: flash: common: use code from sdk-zephyr

All testcases work now, source can be switched to zephyr.

Signed-off-by: Marcin Szymczyk <marcin.szymczyk@nordicsemi.no>

Author: masz-nordic

tests/zephyr/drivers/flash/common/CMakeLists.txt

@@ -4,4 +4,4 @@ cmake_minimum_required(VERSION 3.20.0)
 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(nrf_qspi_nor)
 
-target_sources(app PRIVATE src/main.c)
+target_sources(app PRIVATE ${ZEPHYR_BASE}/tests/drivers/flash/common/src/main.c)