No-cache SRAM section is currently used for ARM-only builds
with support for no-cacheable memory sections (i.e.
CONFIG_ARCH_HAS_NOCACHE_MEMORY_SUPPORT) and it holds
uninitialized data. This commit properly defines the
corresponding linker section using SECTION_DATA_PROLOGUE
and GROUP_DATA_LINK_IN macros.
Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>