[PATCH] bcm43xx: Fix problem with >1 GB RAM

Some versions of the bcm43xx chips only support 30-bit DMA, which means
that the descriptors and buffers must be in the first 1 GB of RAM. On
the i386 and x86_64 architectures with more than 1 GB RAM, an incorrect
assignment may occur. This patch ensures that the various DMA addresses
are within the capability of the chip. Testing has been limited to x86_64
as no one has an i386 system with more than 1 GB RAM.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>