Kconfig: Add missing quotes around source file

All errors are generated by ./tools/qconfig.py -b -j8 -i whatever.
Error look like this:
drivers/crypto/Kconfig:9: warning: style: quotes recommended around
'drivers/crypto/nuvoton/Kconfig' in 'source drivers/crypto/nuvoton/Kconfig'

Signed-off-by: Michal Simek <michal.simek@amd.com>