libbsp/arm: Add the TTB table to the default MMU set up as read/write.

This lets the table be changed at runtime for dynamic loading and
debugger support.

Closes #2775.

c/src/lib/libbsp/arm/shared/include/arm-cp15-start.h

@@ -84,6 +84,10 @@ typedef struct {
     .begin = (uint32_t) bsp_section_nocache_begin, \
     .end = (uint32_t) bsp_section_nocache_end, \
     .flags = ARMV7_MMU_DEVICE \
+  }, { \
+    .begin = (uint32_t) bsp_translation_table_base, \
+    .end = (uint32_t) bsp_translation_table_end, \
+    .flags = ARMV7_MMU_DATA_READ_WRITE_CACHED \
   }
 
 BSP_START_DATA_SECTION extern const arm_cp15_start_section_config