dmaengine: dw-edma: fix unnecessary stack usage

dmaengine: dw-edma: fix unnecessary stack usage

Putting large constant data on the stack causes unnecessary overhead
and stack usage:

drivers/dma/dw-edma/dw-edma-v0-debugfs.c:285:6: error: stack frame size of 1376 bytes in function 'dw_edma_v0_debugfs_on' [-Werror,-Wframe-larger-than=]

Mark the variable 'static const' in order for the compiler to move it
into the .rodata section where it does no such harm.

Fixes: 305aebeff879 ("dmaengine: Add Synopsys eDMA IP version 0 debugfs support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Link: https://lore.kernel.org/r/20190722124457.1093886-1-arnd@arndb.de
Signed-off-by: Vinod Koul <vkoul@kernel.org>