loader: Remove trampoline/terminator dependency in vkEnumeratePhysicalDevices

loader: Remove trampoline/terminator dependency in vkEnumeratePhysicalDevices

There was a dependency between the trampoline vkEnumeratePhysicalDevices
and the terminator vkEnumeratePhysicalDevices via the
loader_instance.phys_devs_term array which may break layers that
manipulate the enumerated VkPhysicalDevice list. This dependency assumed
the devices in loader_instance.phys_devs_term and
loader_instance.phys_devs were in the same order and that it could
assume the index of one corresponding to the same VkPhysicalDevice of
the other.

Breaking this dependency allows layers to modify or reorder the
VkPhysicalDevice list by intercepting the vkEnumeratePhysicalDevices
function without causing the loader to crash. In general, there should
never be a dependency between the trampoline code and the terminator
code because it has the potential to break unknown layers between them.

Conflicts:
	loader/loader.c
	loader/trampoline.c

Change-Id: Iafefd6e8b7dd58d398a76533f957123242c01b56