dmaengine: idxd: make idxd_register/unregister_dma_channel() static

Since idxd_register/unregister_dma_channel() are only called locally, make
them static.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/165187583222.3287435.12882651040433040246.stgit@djiang5-desk3.ch.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>