lib/bootmem: allow architecture specific bootmem ranges

A architecture-specific function, named bootmem_arch_add_ranges(),
is added so that each architecture can add entries into the bootmem
memory map. This allows for a common write_tables() implementation
to avoid code duplication.

Change-Id: I834c82eae212869cad8bb02c7abcd9254d120735
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/14434
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/include/bootmem.h

@@ -26,6 +26,9 @@
  */
 void bootmem_init(void);
 
+/* Architecture hook to add bootmem areas the architecture controls. */
+void bootmem_arch_add_ranges(void);
+
 /* Add a range of a given type to the bootmem address space. */
 void bootmem_add_range(uint64_t start, uint64_t size, uint32_t type);