ALSA: au88x0: Fix incorrect error handling for PCI config reads

ALSA: au88x0: Fix incorrect error handling for PCI config reads

__snd_vortex_probe() uses pci_read_config_word() that returns PCIBIOS_*
codes (positive values on error). However, the function checks 'err < 0'
which can never be true for PCIBIOS_* codes, causing errors to be silently
ignored.

Check for non-zero return value and convert PCIBIOS_* codes using
pcibios_err_to_errno() into normal errno before returning them.

Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
Reviewed-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20251117065559.1138-1-vulab@iscas.ac.cn
Signed-off-by: Takashi Iwai <tiwai@suse.de>