ARM: pxa: fix section mismatch warning for pxa_timer_nodt_init

commit a38b1f60 ("ARM: pxa: Add non device-tree timer link to
clocksource") introduced a harmless section mismatch warning for
all pxa platforms, by introducing a new pxa_timer_init() function
that is not marked __init but that calls pxa_timer_nodt_init(),
which is.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>