ARM: 6677/1: SPEAr: add IOMEM(x) definition and update declaration of MISC_BASE

Add IOMEM(x) definition, and use it with MISC_BASE for SPEAr platform.
With this there is no need to typecast misc macros to (unsigned int *).

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