scripts/checkkconfigsymbols.sh: replace echo -e with printf

-e is a non-standard echo option, echo output is
implementation-dependent when it is used. Replace echo -e
with printf as suggested by POSIX echo manual.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>