ramips: Introduce CONFIG_MIPS_APPENDED_RAW_DTB to arch/mips/ralink

This commit introduces CONFIG_MIPS_APPENDED_RAW_DTB as an alternative to
OWRTDTB. Both solutions can be used concurrently until all board
configurations have been changed.

Signed-off-by: Tobias Wolf <github-NTEO@vplace.de>
[Jo-Philipp Wich: rewrap commit message]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>

target/linux/ramips/patches-4.4/997-ralink-Introduce-fw_passed_dtb-to-arch-mips-ralink.patch

@@ -0,0 +1,28 @@
+--- a/arch/mips/ralink/of.c
++++ b/arch/mips/ralink/of.c
+@@ -81,13 +81,23 @@
+ 
+ void __init plat_mem_setup(void)
+ {
++	void *dtb = NULL;
++
+ 	set_io_port_base(KSEG1);
+ 
+ 	/*
+ 	 * Load the builtin devicetree. This causes the chosen node to be
+-	 * parsed resulting in our memory appearing
++	 * parsed resulting in our memory appearing. fw_passed_dtb is used
++	 * by CONFIG_MIPS_APPENDED_RAW_DTB as well.
+ 	 */
+-	__dt_setup_arch(&__image_dtb);
++	if (fw_passed_dtb)
++		dtb = (void *)fw_passed_dtb;
++	else if (__dtb_start != __dtb_end)
++		dtb = (void *)__dtb_start;
++	else
++		dtb = &__image_dtb;
++
++	__dt_setup_arch(dtb);
+ 
+ 	of_scan_flat_dt(early_init_dt_find_chosen, NULL);
+ 	if (chosen_dtb)