MIPS: ip32, ip27, jazz: Make static functions in dma-coherence.h inline.

Any function defined in a header file should be inline.  This helps us
avoid 'unused' compiler warnings when we include the files in more
places in subsequent patches.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Patchwork: http://patchwork.linux-mips.org/patch/1636/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>