Fixe the following warnings by making these static

drivers/dma/ti/k3-psil-j721e.c:62:16: warning: symbol 'j721e_src_ep_map' was not declared. Should it be static?
drivers/dma/ti/k3-psil-j721e.c:172:16: warning: symbol 'j721e_dst_ep_map' was not declared. Should it be static?
drivers/dma/ti/k3-psil-j721e.c:216:20: warning: symbol 'j721e_ep_map' was not declared. Should it be static?
  CC      drivers/dma/ti/k3-psil-j721e.o
drivers/dma/ti/k3-psil-am654.c:52:16: warning: symbol 'am654_src_ep_map' was not declared. Should it be static?
drivers/dma/ti/k3-psil-am654.c:127:16: warning: symbol 'am654_dst_ep_map' was not declared. Should it be static?
drivers/dma/ti/k3-psil-am654.c:169:20: warning: symbol 'am654_ep_map' was not declared. Should it be static?
Reported-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200121070104.4393-1-peter.ujfalusi@ti.com
[vkoul: updated patch title]
Signed-off-by: Vinod Koul <vkoul@kernel.org>