Remove rt_svc_descs pointer from inner scope

A pointer to rt_svc_desc_t was defined both in the
function and globally. The innermost definition
hid the global definition which is the one we want
to use so remove the innermost definition to prevent
this

Change-Id: Idabdbc0947178ae83224bd17a9b170df7c278d51
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>