Build: Fix cmake implicitly converting warnings

Fix warnings of the form:

	implicitly converting 'bool' to 'STRING' type.
	implicitly converting 'internal' to 'STRING' type.
	implicitly converting 'string' to 'STRING' type.

by changing the type to STRING.

Change-Id: I888126809cd0b9ae4841585979f8ebed6e357160
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
1 file changed