ARM: 7096/1: debug: Add UART1 config choices

ARM patch 7072/1 (debug: use kconfig choice for selecting
DEBUG_LL UART) didn't notice that the Kconfigs relied on being
unselected to configure a different serial port. Since there is
no NONE option in a choice menu, explicitly add the other option
so that both serial ports can be selected.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>