loader: allow attempting more than one method of PCI identification.
loader: allow attempting more than one method of PCI identification.

loader_get_pci_id_for_fd() and loader_get_device_name_for_fd() now attempt
all available strategies to identify the hardware, instead of conditionally
compiling in a single test.  The existing libudev and DRM approaches have
been retained, attempting first libudev (if available) and then DRM (if
necessary).

Signed-off-by: Gary Wong <ae677ff2c1778a216476a0e212c1209b554616e5@gnu.org>
Reviewed-by: Emil Velikov <4c996f2f093ddd0585a556460b4cc3ba555546ef@gmail.com>

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