[PATCH] drivers/net/wireless/airo.c unsigned comparason

fid is declared as a u32 (unsigned int), and then a few lines later, it is checked for a value < 0, which is clearly useless.
In the two locations this function is used, in one it is *explicitly* given a negative number, which would be ignored with the
current definition.

Thanks to LinuxICC (http://linuxicc.sf.net).

Signed-off-by: Gabriel A. Devenyi <ace@staticwave.ca>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>