makedevs: allow leading whitespace for capabilities

makedevs: allow leading whitespace for capabilities

Currently makedevs silently ignores extended attributes with leading
whitespace, for example those added to a <PACKAGE>_PERMISSIONS following
the recommended style from check-package.

Makedevs already ignores leading whitespace for normal entries (file
permission changes and device files creation). Do the same for extended
attributes.

Fixes: #11191.
Reported-by: Jean-pierre Cartal <jpcartal@free.fr>
Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>