MLECO-5105: cmsis_device target updates

Minor change to `cmsis_device` target with the `CMSIS_device_header`
definition used instead of `CPU_HEADER_FILE`. This is done to help
with portability as other related repositories use this specific
definition.

Some other changes have been made to address concerns about cyclic
dependency on platform headers from VSI camera interface. Platform
driver target will not add header path to cmsis_device target so the
VSI CMake file doesn't need to know/guess path to platform-drivers
target to get to IRQ definitions it needs.

Change-Id: Ia6b4d22bcdfb1f44886be7afbd00f53fcbc057ee
Signed-off-by: Kshitij Sisodia <kshitij.sisodia@arm.com>