platform/x86/intel/speed_select_if: Convert PCIBIOS_* return codes to errnos

platform/x86/intel/speed_select_if: Convert PCIBIOS_* return codes to errnos

isst_if_probe() uses pci_read_config_dword() that returns PCIBIOS_*
codes. The return code is returned from the probe function as is but
probe functions should return normal errnos. A proper implementation
can be found in drivers/leds/leds-ss4200.c.

Convert PCIBIOS_* return codes using pcibios_err_to_errno() into
normal errno before returning.

Fixes: d3a23584294c ("platform/x86: ISST: Add Intel Speed Select mmio interface")
Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/20251117033354.132-1-vulab@iscas.ac.cn
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>