mips: fix dynamic ftrace

The kernel patch *-mips_module_reloc.patch breaks dynamic ftrace as
dynamic ftrace depends on -mlong-calls.
See http://patchwork.linux-mips.org/patch/675/
Thus we always set -mlong-calls if the kernel is being
compiled with dynamic ftrace support.

Signed-off-by: Vincent Wiemann <webmaster@codefetch.de>

target/linux/generic/pending-4.9/305-mips_module_reloc.patch

@@ -11,7 +11,7 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
 
 --- a/arch/mips/Makefile
 +++ b/arch/mips/Makefile
-@@ -93,8 +93,13 @@ all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlin
+@@ -93,8 +93,18 @@ all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlin
  cflags-y			+= -G 0 -mno-abicalls -fno-pic -pipe -mno-branch-likely
  cflags-y			+= -msoft-float
  LDFLAGS_vmlinux			+= -G 0 -static -n -nostdlib
@@ -19,8 +19,13 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  KBUILD_AFLAGS_MODULE		+= -mlong-calls
  KBUILD_CFLAGS_MODULE		+= -mlong-calls
 +else
-+KBUILD_AFLAGS_MODULE		+= -mno-long-calls
-+KBUILD_CFLAGS_MODULE		+= -mno-long-calls
++  ifdef CONFIG_DYNAMIC_FTRACE
++    KBUILD_AFLAGS_MODULE	+= -mlong-calls
++    KBUILD_CFLAGS_MODULE	+= -mlong-calls
++  else
++    KBUILD_AFLAGS_MODULE	+= -mno-long-calls
++    KBUILD_CFLAGS_MODULE	+= -mno-long-calls
++  endif
 +endif
  
  ifeq ($(CONFIG_RELOCATABLE),y)