[CORE] vmm_devtree: Introduce built-in nodeid table

This patch introduces a special nodeid table which is built-in in
the Xvisor binary at compile time.

Various driver or emulator frameworks can use it to provide custom
macros for having compile time registration of resources.

For example, the common device tree based clocking framework will use
it to provide linux-like CLK_OF_DECLARE() macro which will be used by
clocking drivers to register Clock Providers at compile time. Appropriate
clock provider is probed based on clock nodes in the DTB file provided
to Xvisor.

Currently people will have to use the VMM_DEVTREE_NODEID_TABLE_ENTRY()
macro to add an entry to built-in nodeid table. Please note that
VMM_DEVTREE_NODEID_TABLE_ENTRY() is only available to code directly
linked with Xvisor binary. In future, we will also support the
VMM_DEVTREE_NODEID_TABLE_ENTRY() for pluggable macros but for now
we don't need to support it for pluggable modules.

Signed-off-by: Anup Patel <anup@brainfault.org>