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-4.1/307-mips_highmem_offset.patch

@@ -0,0 +1,17 @@
+Adjust highmem offset to 0x10000000 to ensure that all kmalloc allocations
+stay within the same 256M boundary. This ensures that -mlong-calls is not
+needed on systems with more than 256M RAM.
+
+Signed-off-by: Felix Fietkau <nbd@openwrt.org>
+---
+--- a/arch/mips/include/asm/mach-generic/spaces.h
++++ b/arch/mips/include/asm/mach-generic/spaces.h
+@@ -44,7 +44,7 @@
+  * Memory above this physical address will be considered highmem.
+  */
+ #ifndef HIGHMEM_START
+-#define HIGHMEM_START		_AC(0x20000000, UL)
++#define HIGHMEM_START		_AC(0x10000000, UL)
+ #endif
+ 
+ #endif /* CONFIG_32BIT */