powerpc/uaccess: Remove __unsafe_put_user_goto()

__unsafe_put_user_goto() is just an intermediate layer to
__put_user_size_goto() without added value other than doing
the __user pointer type checking.

Do the __user pointer type checking in __put_user_size_goto()
and remove __unsafe_put_user_goto().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b6552149209aebd887a6977272b06a41256bdb9f.1615398265.git.christophe.leroy@csgroup.eu