staging: dgnc: cls_uart_struct: adds marker and changes vars' types for sparse

This patch removes these sparse warnings found in the cls.c file:

warning: incorrect type in argument 1 (different address spaces)
  expected void const volatile [noderef] <asn:2>*addr
  got unsigned char volatile *<noident>
warning: incorrect type in argument 2 (different address spaces)
  expected void volatile [noderef] <asn:2>*addr
  got unsigned char volatile *<noident>

The variables passed to readb and writeb need to
be of type u8 with a __iomem marker. These warnings
were popping up everytime the readb and writeb
functions were called with a cls_uart_struct variable.

The change made to the driver.h file adds the marker
to the cls_uart_struct and the changes in cls.h
changes its variables' types.

Signed-off-by: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>