arm64: include asm/assembler.h in entry-ftrace.S

In a randconfig build I ran into this build error:

arch/arm64/kernel/entry-ftrace.S: Assembler messages:
arch/arm64/kernel/entry-ftrace.S:101: Error: unknown mnemonic `ldr_l' -- `ldr_l x2,ftrace_trace_function'

The macro is defined in asm/assembler.h, so we should include that file.

Fixes: 829d2bd1 ("arm64: entry-ftrace.S: avoid open-coded {adr,ldr}_l")
Acked-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch/arm64/kernel/entry-ftrace.S

@@ -10,6 +10,7 @@
  */
 
 #include <linux/linkage.h>
+#include <asm/assembler.h>
 #include <asm/ftrace.h>
 #include <asm/insn.h>