arm: k3: fix fdt_del_node_path implicit declaration and a missing include

Fix missing declaration of fdt_del_node_path() while compiling am625_fdt.c and
missing common_fdt.h include in common_fdt.c

Fixes: 70aa5a94 ("arm: mach-k3: am62: Fixup CPU core, gpu and pru nodes in fdt")
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>