ARM: 6928/1: SPEAr3xx: Make local shirq structures static

Several structures in arch/arm/mach-spear3xx are not marked static
like they should be. Fix this.

Reviewed-by: Stanley Miao <stanley.miao@windriver.com>
Signed-off-by: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>