ALSA: trivial: sound seq ioctl dbg: print hexadecimal value padded with 0s

Instead of padding with blanks and printing "number=0x a", print
"number=0x0a".

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>