x86: reducing debuginfo size by removing unneeded includes

	I found it strange that the struct sk_buff definition was found
inside the DWARF debugging sections in the generated object, so I verified
and found that there is no need for the files that bring struct sk_buff
definition into this file and verified also that sk_buff is not brought
in indirectly too, thru other headers.

	I went on and removed many other unneeded includes and the end
result is:

[acme@doppio net-2.6]$ l /tmp/sys_ia32.o.before /tmp/sys_ia32.o.after
-rw-rw-r-- 1 acme acme 185240 2008-02-06 19:19 /tmp/sys_ia32.o.after
-rw-rw-r-- 1 acme acme 248328 2008-02-06 19:00 /tmp/sys_ia32.o.before

	Almost 64KB only on this object file!

	There were no other side effects from this change:

[acme@doppio net-2.6]$ objcopy -j "text" /tmp/sys_ia32.o.before /tmp/text.before
[acme@doppio net-2.6]$ objcopy -j "text" /tmp/sys_ia32.o.after /tmp/text.after
[acme@doppio net-2.6]$ md5sum /tmp/text.before /tmp/text.after
b7ac9b17942add68494e698e4f965d36  /tmp/text.before
b7ac9b17942add68494e698e4f965d36  /tmp/text.after

	One of the complaints about using tools such as systemtap is
that one has to install the huge kernel-debuginfo package:

[acme@doppio net-2.6]$ rpm -q --qf "%{size}\n" kernel-rt-debuginfo
471737710
543867594
[acme@doppio net-2.6]$

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>