ARM: cache_v7: use __weak

This is not only more readable but also prevents a warning
about a missing prototype. The prototypes which are actually
missing are added.

cc: Albert Aribaud <albert.u.boot@aribaud.net>
Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>
Reviewed-by: Tom Rini <trini@ti.com>

arch/arm/include/asm/cache.h

@@ -29,6 +29,9 @@ void l2_cache_enable(void);
 void l2_cache_disable(void);
 void set_section_dcache(int section, enum dcache_option option);
 
+void arm_init_before_mmu(void);
+void arm_init_domains(void);
+void cpu_cache_initialization(void);
 void dram_bank_mmu_setup(int bank);
 
 #endif