ALSA: core/seq: Optimize the return logic in cc_ev_to_ump_midi2

ALSA: core/seq: Optimize the return logic in cc_ev_to_ump_midi2

There are multiple early return branches within the func, and compiler
optimizations(such as -O2/-O3)lead to abnormal stack frame analysis -
objtool cannot comfirm that the stack frames of all branches can be
correctly restored, thus generating false warnings.

Below:
>> sound/core/seq/seq_ump_convert.o: warning: objtool: cc_ev_to_ump_midi2+0x589: return with modified stack frame

So we modify it by uniformly returning at the and of the function.

Signed-off-by: songxiebing <songxiebing@kylinos.cn>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202503200535.J3hAvcjw-lkp@intel.com/
Link: https://patch.msgid.link/20260325015119.175835-1-songxiebing@kylinos.cn
Signed-off-by: Takashi Iwai <tiwai@suse.de>