doc: coverage: fix coverage report generation instruction
doc: coverage: fix coverage report generation instruction

Fix build step to enable CONFIG_COVERAGE_DUMP, otherwise
we won't get coverage data dump required for next step.

Signed-off-by: Evgeniy Paltsev <7de4ab8b01334d64e4e84734c688a8a936513edc@gmail.com>
Signed-off-by: Eugeniy Paltsev <ec089b543c2604b626d7ce60c03e4d074ed102c7@synopsys.com>

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