generic: add linux 4.1 support

Boot tested: http://pastebin.com/L6aAb9xj

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
[jogo:
  update to 4.1 final
  add patches added since submission
  delete patches applied in later rcs
  restore commit messages in 220-gc-sections and 304-mips_disable_fpu
  fix 050-backport_netfilter_rtcache to match new API
  update inlined dma ops with upstream changes
  add missing config symbols
  enabled CONFIG_MULTIUSER
  update kmod defintions for 4.1
]
Signed-off-by: Jonas Gorski <jogo@openwrt.org>

SVN-Revision: 46112

target/linux/generic/patches-4.1/921-use_preinit_as_init.patch

@@ -0,0 +1,12 @@
+--- a/init/main.c
++++ b/init/main.c
+@@ -959,7 +959,8 @@ static int __ref kernel_init(void *unuse
+ 		panic("Requested init %s failed (error %d).",
+ 		      execute_command, ret);
+ 	}
+-	if (!try_to_run_init_process("/sbin/init") ||
++	if (!try_to_run_init_process("/etc/preinit") ||
++	    !try_to_run_init_process("/sbin/init") ||
+ 	    !try_to_run_init_process("/etc/init") ||
+ 	    !try_to_run_init_process("/bin/init") ||
+ 	    !try_to_run_init_process("/bin/sh"))