Staging: d53155_drv.c: cleanup fbuffer usage

The global symbol dt3155_fbuffer[], declared in dt3155_isr.c, is really
just a pointer to dt3155_status[].fbuffer. To improve readability, make
some of the really long lines shorter, and make the buffer access more
consistent, use &dt3155_status[].fbuffer to access the buffer structure.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Scott Smedley <ss@aao.gov.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>