include/bootmem.h: Add comment

Signed-off-by: Maximilian Brune <maximilian.brune@9elements.com>
Change-Id: I8f6752e887af8c1ceba56153e3da864abd040ffa
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79947
Reviewed-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/bootmem.h

@@ -46,6 +46,7 @@ enum bootmem_type {
  * BM_MEM_RAMSTAGE : Translates to LB_MEM_RAM.
  * BM_MEM_PAYLOAD  : Translates to LB_MEM_RAM.
  * BM_MEM_BL31     : Translates to LB_MEM_RESERVED.
+ * BM_MEM_OPENSBI  : Translates to LB_MEM_RESERVED.
  */
 void bootmem_write_memory_table(struct lb_memory *mem);