ARM: 6637/1: Make the argument to virt_to_phys() "const volatile"

Changing the virt_to_phys() argument to "const volatile void *" avoids
compiler warnings in some situations where this function is used.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>