testsuite: coverage: application unable to include `coverage.h`

[ycsin]

Describe the bug

Application should be able to include the private header coverage.h that is conditionally exposed when CONFIG_COVERAGE_GCOV=y by:

#include "coverage"

but since there is a typo in the CMakeLists.txt, it is not able to do so:

zephyr/subsys/testsuite/CMakeLists.txt

Line 9 in 193eeae

zephyr_include_directories_ifdef(CONFIG_COVERAGE_GCOV ${zephyr_BASE}/subsys/testsuite/coverage)

Specifically, the zephyr_BASE variable should be ZEPHYR_BASE instead.

To Reproduce
Steps to reproduce the behavior:

1. Enable CONFIG_COVERAGE_GCOV and try to include the coverage.h in an application
2. west build ...
3. See error

Expected behavior
Compilation should pass

Impact
Application can't include the coverage.h, otherwise the compilation fails.

Environment (please complete the following information):

• OS: Linux
• Toolchain: Zephyr SDK
• Commit SHA or Version used: 193eeae