It allows us to make things a little bit more generic. Also, we now
require fd rather than doing guesswork when it comes to pci address.
v2: Use readlinkat rather than string concat, move stuff around, provide
a version that does not assert. (Chris)
v3: Print addr on failure, avoid assignment in conditionals. (Chris)
Signed-off-by: Michał Winiarski <firstname.lastname@example.org>
Cc: Chris Wilson <email@example.com>
Reviewed-by: Chris Wilson <firstname.lastname@example.org>