arm/bsps: Small MMU pages are rounded to 1 MiB (cloned)

Original author: soja

Cloned from #4184 (closed):

The function arm_cp15_start_set_translation_table_entries rounds the end address of a section up to 1 MiB even if small 4kiB pages are used (i.e. ARM_MMU_USE_SMALL_PAGES enabled).

Will submit a patch which only rounds the end address to 4kiB boundary.