twa(4) doesn't depend on cam(4) and pci(4).

Hi Vinod.

	I found a bug that twa(4)'s module doesn't depend on cam(4)
	and pci(4).  Please commit following patch and MFC.

	I think that there are same bugs in many driver depended on
	cam(4) like advansys(4), aha(4), ahb(4), amr(4), arcmsr(4),
	asr(4), ....
	I confirmed following way:  (compare following result)
	# cd /usr/src/sys/dev
	# fgrep -l xpt_ */*.c
	# fgrep MODULE_DEPEND `fgrep -l xpt_ */*.c`
	So I might miss.

Index: tw_osl_freebsd.c
===================================================================
RCS file: /home/ncvs/src/sys/dev/twa/tw_osl_freebsd.c,v
retrieving revision 1.4
diff -u -r1.4 tw_osl_freebsd.c
--- tw_osl_freebsd.c	8 Nov 2005 22:51:43 -0000	1.4
+++ tw_osl_freebsd.c	23 Mar 2006 12:20:29 -0000
_at__at_ -207,6 +207,8 _at__at_
 };
 
 DRIVER_MODULE(twa, pci, twa_pci_driver, twa_devclass, 0, 0);
+MODULE_DEPEND(sym, cam, 1, 1, 1);
+MODULE_DEPEND(sym, pci, 1, 1, 1);