Fix typo in ada_language_arch_info

Fix typo in ada_language_arch_info

This fixes a bug introduced by a wrong replacement here:
https://sourceware.org/ml/gdb-patches/2007-06/msg00196.html

The Ada "long_long_float" type is supposed to correspond to the
platform ABI long double type, not double.

gdb/ChangeLog:

	* ada-lang.c (ada_language_arch_info): Use gdbarch_long_double_bit
	instead of gdbarch_double_bit for "long_long_float".

Signed-off-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>