arm: Fix typo in spear3[012]0.c

Correct spelling "registeration" to "registration" in
arch/arm/mach-spear3xx/spear300.c, spear310.c and spear320.c

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>