arm64: Remove reference to asm/opcodes.h

The asm/opcodes.h file is now gone, but probes.h still references it
for not obvious reason. Removing the #include directive fixes
the compilation.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>