powerpc/configs: Update for CONFIG_INPUT_MOUSEDEV=n

In commit 73d8ef76 ("Input: mousedev - stop offering PS/2 to
userspace by default") the symbol INPUT_MOUSEDEV went from being
'default y' to 'default n' (implied).

That means we no longer need to explicitly disable it in our
defconfigs.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>