staging: kpc2000: Fix: 'kpc_dma_del_device' and other symbols were not declared

This patch removes the Sparse generated warnings. Following warnings are reported by Sparse:
drivers/staging/kpc2000//kpc_dma/kpc_dma_driver.c:46:6: warning: symbol 'kpc_dma_del_device' was not declared. Should it be static?
drivers/staging/kpc2000//kpc_dma/kpc_dma_driver.c:91:14: warning: symbol 'kpc_dma_class' was not declared. Should it be static?
drivers/staging/kpc2000//kpc_dma/kpc_dma_driver.c:199:24: warning: symbol 'kpc_dma_plat_driver_i' was not declared. Should it be static?

Signed-off-by: Rishiraj Manwatkar <manwatkar@outlook.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>