arm64: kexec_file: include linux/vmalloc.h

This is needed for compilation in some configurations that don't
include it implicitly:

arch/arm64/kernel/machine_kexec_file.c: In function 'arch_kimage_file_post_load_cleanup':
arch/arm64/kernel/machine_kexec_file.c:37:2: error: implicit declaration of function 'vfree'; did you mean 'kvfree'? [-Werror=implicit-function-declaration]

Fixes: 52b2a8af ("arm64: kexec_file: load initrd and device-tree")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/machine_kexec_file.c

@@ -19,6 +19,7 @@
 #include <linux/random.h>
 #include <linux/string.h>
 #include <linux/types.h>
+#include <linux/vmalloc.h>
 #include <asm/byteorder.h>
 
 /* relevant device tree properties */