staging: brcm80211: remove W_SM and R_SM macros from dma.c

The macros W_SM and R_SM are not doing much conversion of the macro
parameters and complicate code readability without good cause. It
is more clear to remove usage of the macros expanding it in the source
code.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Henry Ptasinski <henryp@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>