Fix MIPS gdbserver to look for DT_MIPS_RLD_MAP instead of DT_DEBUG

Backport of fixes

    2012-04-10  Maciej W. Rozycki  <macro@codesourcery.com>

	* linux-low.c (get_r_debug): Handle DT_MIPS_RLD_MAP.

    2012-05-30  Thiago Jung Bauermann  <thiago.bauermann@linaro.org>

	* linux-low.c (get_r_debug): Disable code using DT_MIPS_RLD_MAP
	if the platform doesn't know about it.

See http://www.sourceware.org/ml/gdb-patches/2012-04/msg00055.html

Change-Id: I83fa3e0d60095bac4cbd9c784a846f0189008474