ARM: at91: fix broken "if () else" statement

If CONFIG_PATA_AT91 is disabled, the code in at91_add_device_cf
is turned into invalid C statements due to the lack of an
expression before the 'else' clause.

This moves the first half of the condition inside of the #ifdef,
which seems to be what the author intended.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>