dmaengine: dw-edma: increase size of 'name' in debugfs code

We seem to have hit warnings of 'output may be truncated' which is fixed
by increasing the size of 'name'

drivers/dma/dw-edma/dw-hdma-v0-debugfs.c: In function ‘dw_hdma_v0_debugfs_on’:
drivers/dma/dw-edma/dw-hdma-v0-debugfs.c:125:50: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 8 [-Werror=format-truncation=]
  125 |                 snprintf(name, sizeof(name), "%s:%d", CHANNEL_STR, i);
      |                                                  ^~

drivers/dma/dw-edma/dw-hdma-v0-debugfs.c: In function ‘dw_hdma_v0_debugfs_on’:
drivers/dma/dw-edma/dw-hdma-v0-debugfs.c:142:50: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 8 [-Werror=format-truncation=]
  142 |                 snprintf(name, sizeof(name), "%s:%d", CHANNEL_STR, i);
      |                                                  ^~
drivers/dma/dw-edma/dw-edma-v0-debugfs.c: In function ‘dw_edma_debugfs_regs_wr’:
drivers/dma/dw-edma/dw-edma-v0-debugfs.c:193:50: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 8 [-Werror=format-truncation=]
  193 |                 snprintf(name, sizeof(name), "%s:%d", CHANNEL_STR, i);
      |                                                  ^~

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