powerpc: Fix bad NULL pointer check in udbg_uart_getc_poll()

powerpc: Fix bad NULL pointer check in udbg_uart_getc_poll()

commit cd32e2dcc9de6c27ecbbfc0e2079fb64b42bad5f upstream.

We have some code in udbg_uart_getc_poll() that tries to protect
against a NULL udbg_uart_in, but gets it all wrong.

Found with the LLVM static analyzer (scan-build).

Fixes: 309257484cc1 ("powerpc: Cleanup udbg_16550 and add support for LPC PIO-only UARTs")
Signed-off-by: Anton Blanchard <anton@samba.org>
[mpe: Add some newlines for readability while we're here]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>