MIPS: generic: Support booting with built-in or appended DTB

The plat_get_fdt() checked that the kernel was booted using UHI before
reading the 'fw_passed_dtb' variable. However, this variable is also set
when the DT has been appended, or when it has been built into the kernel.

Support these usecases by removing the UHI check.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/generic/init.c

@@ -39,12 +39,11 @@ void __init *plat_get_fdt(void)
 		/* Already set up */
 		return (void *)fdt;
 
-	if ((fw_arg0 == -2) && !fdt_check_header((void *)fw_passed_dtb)) {
+	if (fw_passed_dtb && !fdt_check_header((void *)fw_passed_dtb)) {
 		/*
-		 * We booted using the UHI boot protocol, so we have been
-		 * provided with the appropriate device tree for the board.
-		 * Make use of it & search for any machine struct based upon
-		 * the root compatible string.
+		 * We have been provided with the appropriate device tree for
+		 * the board. Make use of it & search for any machine struct
+		 * based upon the root compatible string.
 		 */
 		fdt = (void *)fw_passed_dtb;