bcm63xx: copy files to kernel 5.4

Copy config and patches to kernel 5.4.
make kernel_oldconfig has been run on 4.19 beforehand.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/bcm63xx/patches-5.4/310-cfe_simplify_detection.patch

@@ -0,0 +1,20 @@
+--- a/arch/mips/include/asm/mach-bcm63xx/bcm63xx_board.h
++++ b/arch/mips/include/asm/mach-bcm63xx/bcm63xx_board.h
+@@ -2,6 +2,8 @@
+ #ifndef BCM63XX_BOARD_H_
+ #define BCM63XX_BOARD_H_
+ 
++#include <asm/bootinfo.h>
++
+ const char *board_get_name(void);
+ 
+ void board_prom_init(void);
+@@ -10,4 +12,8 @@ void board_setup(void);
+ 
+ int board_register_devices(void);
+ 
++static inline bool bcm63xx_is_cfe_present(void) {
++	return fw_arg3 == 0x43464531;
++}
++
+ #endif /* ! BCM63XX_BOARD_H_ */