irq: versatile: rename Kconfig macro in printk

Commit 2389d501 ("ARM: plat-versatile:
move FPGA irq driver to drivers/irqchip") changed Kconfig symbol
PLAT_VERSATILE_FPGA_IRQ_NR to VERSATILE_FPGA_IRQ_NR. It forgot to change
one reference to the related macro in a printk.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>