ALSA: lx6464es: add error handling for pci_ioremap_bar

When pci_ioremap_bar fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling pci_ioremap_bar.

Signed-off-by: Zhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>