elflink: Delete obsolete constructor code

elflink: Delete obsolete constructor code

Since commit 8e0ed96bff75 ("elf: Support __constructor and
__destructor") the code for looping over ctors in ldlinux has been
unnecessary. Delete since this is all now handled in the core module
loading code.

This also gets rid of the following build warning,

elflink/load_env32.c: At top level:
elflink/load_env32.c:28:15: warning: array ‘__ctors_start’ assumed to have one element
elflink/load_env32.c:28:32: warning: array ‘__ctors_end’ assumed to have one element

Signed-off-by: Matt Fleming <matt.fleming@intel.com>