Fix readline_into_buffer() with CONFIG_CMDLINE_EDITING before relocating

When CONFIG_CMDLINE_EDITING is enabled, readline_into_buffer() doesn't
work before relocating to RAM because command history is written into
a global array that is not writable before relocation.  This patch
defers to the no-editing and no-history code in readline_into_buffer()
if it is called before relocation.

Signed-off-by: James Yang <James.Yang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>