drm/radeon: Modernize VFCT error handling

drm/radeon: Modernize VFCT error handling

Clean up radeon_acpi_vfct_bios() logging:

- Replace DRM_ERROR with dev_warn tied to the PCI device
- Use unsigned int rather than bare unsigned for the offset

A malformed or missing VFCT table is not fatal: radeon falls back
to the other BIOS fetch methods, so warn rather than error on these
paths.

The goto out label is retained: acpi_get_table() takes a reference on
the table (incrementing its validation_count and mapping it), which
must be released with a paired acpi_put_table() on every exit path.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patch.msgid.link/20260708193518.702584-4-mario.limonciello@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>