ARM: mmu: Introduce weak dram_bank_setup function

Introduce a weak version of dram_bank_setup function
to allow a platform specific function.

This is used in the subsequent patch to setup dram region
without 'XN' attribute in order to enable the region
under client permissions.

Signed-off-by: R Sricharan <r.sricharan@ti.com>
Cc: Vincent Stehle <v-stehle@ti.com>
Cc: Tom Rini <trini@ti.com>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>

arch/arm/include/asm/cache.h

@@ -43,6 +43,7 @@ void l2_cache_enable(void);
 void l2_cache_disable(void);
 void set_section_dcache(int section, enum dcache_option option);
 
+void dram_bank_mmu_setup(int bank);
 /*
  * The current upper bound for ARM L1 data cache line sizes is 64 bytes.  We
  * use that value for aligning DMA buffers unless the board config has specified