Staging: brcm80211: hnddma.c: fix compiler warning

Change the field types of dma_info_t to make comparing values easier
(and correct.)  No need to keep rxbufsize as a u16, it can be an
unsigned int to make things easier.

Cc: Brett Rudley <brudley@broadcom.com>
Cc: Henry Ptasinski <henryp@broadcom.com>
Cc: Nohee Ko <noheek@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>