i965: Make intel_get_param return an int

i965: Make intel_get_param return an int

This will fix the spurious error message: "Failed to query GPU properties."
that was unintentionally added in cc01b63d730.

This patch changes the function to return an int so that the caller is able to
do stuff based on the return value.

The equivalent of this patch was in the original series that fixed up the
warning, but I dropped it at the last moment. It is required to make the desired
behavior of not warning when trying to query GPU properties from the kernel
unless there is something the user can do about it.

v2: Use strerror (Jason)
Make EINVAL check similar in all places (Ian)

NOTE: Broadwell appears to actually have some issue where the kernel returns
ENODEV when it shouldn't be. I will investigate this separately.

Reported-by: Chris Forbes <chrisf@ijw.co.nz>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>