package/optee-client: rename S30optee

Commit b1c4c187 forgot to rename
S30optee in optee-client.mk resulting in the following build failure:

/usr/bin/install -m 0755 -D package/optee-client//S30optee /home/autobuild/autobuild/instance-0/output-1/target/etc/init.d/S30optee
/usr/bin/install: cannot stat 'package/optee-client//S30optee': No such file or directory

Fixes:
 - http://autobuild.buildroot.org/results/21fc165933e6d226de277b62d4ce99342cef0ffb



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>