package/libgpiod: bump version to 1.4.5

* add a comment about the kernel header dependencies when bumping
versions
* set url to kernel.org as github is unmaintained and outdated
* use two spaces in hash-file

Signed-off-by: Michael Nosthoff <buildroot@heine.tech>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>