linux, package: do not use <pkg>_NAME when defining CPE ID variables

linux, package: do not use <pkg>_NAME when defining CPE ID variables

As we discussed on the mailing list, using $(<pkg>_NAME) when defining
CPE ID variables feels a bit odd and needlessly complicated. Just use
the package name directly.

Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>