ARM: dts: bcm63138: change "interupts" to "interrupts"

all other nodes in bcm63138.dtsi use "interrupts", this had to be just a typo
which never got noticed, even it may have quite some consequences.

Signed-off-by: Radek Dostal <radek.dostal@streamunlimited.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>