kmod: needs largefile

kmod: needs largefile

Since version 20 it requires largefile support.

http://git.kernel.org/cgit/utils/kernel/kmod/kmod.git/commit/?id=481ad14550087c77c9df6d117c7a975a38a4ad33
 - Disable --disable-largefile. We already had possible bugs in the
   index implementation if this were passed. It's now fixed, but it's
   never tested. Disable it.

Fix build failure:
configure: error: --disable-largefile is not supported by kmod
package/pkg-generic.mk:172: recipe for target 'output/build/kmod-20/.stamp_configured' failed

Fixes:
http://autobuild.buildroot.net/results/f662d9230e4bc2da7dc56a2ffd493cc37254d377//
http://autobuild.buildroot.net/results/233ec8ee346e15d41658cffc6bbb4a6c9dd46746//

[Thomas:
 - use two separate 'depends on' conditions for BR2_STATIC_LIBS and
   BR2_LARGEFILE, like we do in most packages.
 - take this opportunity to also indicate the dependency on dynamic
   library in the comment, which was missing until now.]

Signed-off-by: Fabio Porcedda <fabio.porcedda@gmail.com>
Cc: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>