common: Make ARCH_EARLY_INIT_R be selected only

common: Make ARCH_EARLY_INIT_R be selected only

As platforms which require this hook need this hook enabled, in order to
function, or do not need this hook, it doesn't make sense to prompt the
user. As all platforms that need this hook now select the symbol, remove
the prompt text.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>