tests: flash: ite: Add M1K test overlay for it515xx_evb

Add a new overlay for testing the M1K flash controller:

it515xx_m1k.overlay (only supported on it515xx_evb)

Update testcase.yaml to include this overlay with DTC_OVERLAY_FILE
and platform_allow accordingly.

example:
west twister -p it515xx_evb -s drivers.flash.common.it515xx_m1k

Signed-off-by: Tim Lin <tim2.lin@ite.corp-partner.google.com>
2 files changed