tests: drivers: flash: increase write size of test
tests: drivers: flash: increase write size of test

Some SOCs, such as NXP's LPC family, expect a minimum write size of 512
bytes. Increase the EXPECTED_SIZE definition for flash driver test to
512 so that test can pass on these platforms.

Signed-off-by: Daniel DeGrasse <002dd1d4ac44ebb71088aae93501e62b784ed821@nxp.com>

zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr