e1000: Mask out lower bits of RDBAL/TDBAL Rx and Tx descriptors are 16 byte aligned, so the lower bits are ignored by real hardware. In fact, they always read back as zero on real hardware, but probably nobody relies on that. Signed-off-by: Kevin Wolf <mail@kevin-wolf.de> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>