feat(zynqmp): add hooks for mmap and early setup

Add early setup hooks (via custom_early_setup()) and provide a way
to cover custom memory mapping which includes extending memory map
via custom_mmap_add().

This likely also require to align MAX_XLAT_TABLE, MAX_XLAT_TABLES
macros. It can be done for example by defining these macros in
custom_pkg.mk
MAX_MMAP_REGIONS	:= XY
$(eval $(call add_define,MAX_MMAP_REGIONS))
MAX_XLAT_TABLES		:= XZ
$(eval $(call add_define,MAX_XLAT_TABLES))

custom_early_setup() can be used for early low level operations
related to setting up the system to correct state.

Signed-off-by: Amit Nagal <amit.nagal@amd.com>
Change-Id: I61df6f9ba5af0bc97c430974fb10a2edde44f23d
diff --git a/plat/xilinx/zynqmp/include/custom_svc.h b/plat/xilinx/zynqmp/include/custom_svc.h
index 389a7bc..ef0eb67 100644
--- a/plat/xilinx/zynqmp/include/custom_svc.h
+++ b/plat/xilinx/zynqmp/include/custom_svc.h
@@ -13,4 +13,7 @@
 			    uint64_t x3, uint64_t x4, void *cookie,
 			    void *handle, uint64_t flags);
 
+void custom_early_setup(void);
+void custom_mmap_add(void);
+
 #endif /* CUSTOM_SVC_H */