powerpc: Remove superflous function descriptors in assembly only code

We have a number of places where we load the text address of a local
function and indirectly branch to it in assembly. Since it is an
indirect branch binutils will not know to use the function text
address, so that trick wont work.

There is no need for these functions to have a function descriptor
so we can replace it with a label and remove the dot symbol.

Signed-off-by: Anton Blanchard <anton@samba.org>