crda: remove static library handling

In commit d54418f2 ("crda: fix static
build failure"), some static linking handling was added in crda. But
in a later commit, 7c08fa93 ("crda:
needs dynamic library support"), crda was marked as not available for
static only builds.

This means that the static linking logic in crda.mk is now just dead
code, so this commit gets rid of it.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Samuel Martin <s.martin49@gmail.com>