cmd/objdump: update test with register ABI

With register ABI, the disassembly of the function may not
contain a "movq" instruction (which used to be e.g. storing
arguments to stack). Look for "jmp" instruction instead. This is
also in consistent with the test for Go assembly syntax.

Change-Id: Ifc9e48bbc4f85c4e4aace5981b3a0f8ae925f6d6
Reviewed-on: https://go-review.googlesource.com/c/go/+/308652


Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>