libpayload: multiboot - support meminfo flag

Some simple implementation of the MultiBoot protocol may not pass a
memory map (MULTIBOOT_FLAGS_MMAP missing in the flags) but just the two
values for low and high memory, indicated by the MULTIBOOT_FLAGS_MEMINFO
flag.

Support those kind of boot loaders too, instead of falling back to the
hard-coded values in lib_get_sysinfo().

Tested with a multiboot enhanced version of FILO.

Change-Id: I22cf9e3ec0075aff040390bd177c5cd22d439b81
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Reviewed-on: https://review.coreboot.org/18350
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>

payloads/libpayload/include/multiboot_tables.h

@@ -35,6 +35,7 @@
 #define MULTIBOOT_MAGIC      0x2BADB002UL
 #define MULTIBOOT_FLAGS_MMAP    (1 << 6)
 #define MULTIBOOT_FLAGS_CMDLINE (1 << 2)
+#define MULTIBOOT_FLAGS_MEMINFO (1 << 0)
 struct multiboot_header {
 	u32 flags;
 	u32 mem_lower;