net: bcm4358: fix not to check same value in macro

net: bcm4358: fix not to check same value in macro

When BCMBUSTYPE is not defined, then BUSTYPE(bustype) is just
bustype. So comparing bustype and BUSTYPE(bustype) is not necessary.

This patch removes following build warning with gcc 6.
   drivers/net/wireless/bcmdhd4358/siutils.c: In function 'si_doattach':
   drivers/net/wireless/bcmdhd4358/siutils.c:512:14: warning: self-comparison always evaluates to false [-Wtautological-compare]
     if (bustype != BUSTYPE(bustype)) {
                 ^~

Change-Id: I1cac3dd31bcb86983469830013a1093ed9ceaa89
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>