remove various dma_declare_coherent related exports

[Christoph Hellwig]

Hi all,

this is a refresh of and older series that tries to ensure that
drivers don't use the dma_declare_coherent function, which is
intende for platform code.  Unfortunately we've actually grown
a user in remoteproc since then.  While the maintainers havee
promised to fix that up that hasn't happened so far, so for now
this disabled the modular build for remoteproc until that has been
solved.