silicom: checkpatch: errors caused by macros

fixed checkpatch error:
added parenthesis around complex macro.

Macro with return was only used once in the code,
so I expandet it in-place.

Signed-off-by: Lorenz Haspel <lorenz@badgers.com>
Signed-off-by: Michael Banken <michael.banken@mathe.stud.uni-erlangen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>