powerpc/uaccess: Simplify unsafe_put_user() implementation

Currently unsafe_put_user() expands to __put_user_goto(), which
expands to __put_user_nocheck_goto().

There are no other uses of __put_user_nocheck_goto(), and although
there are some other uses of __put_user_goto() those could just use
unsafe_put_user().

Every layer of indirection introduces the possibility that some code
is calling that layer, and makes keeping track of the required
semantics at each point more complicated.

So drop __put_user_goto(), and rename __put_user_nocheck_goto() to
__unsafe_put_user_goto(). The "nocheck" is implied by "unsafe".

Replace the few uses of __put_user_goto() with unsafe_put_user().

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210208135717.2618798-1-mpe@ellerman.id.au