ipw2100: avoid warning from pointer cast in call to IPW_DEBUG_TX

drivers/net/wireless/ipw2x00/ipw2100.c: In function 'ipw2100_tx_send_commands':
drivers/net/wireless/ipw2x00/ipw2100.c:3063: warning: cast to pointer from integer of different size

This changes the cast and the conversion to match other usage of the
same value in calls to IPW_DEBUG_TX.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>