Try reserving less ram...

In 005a0aa, we switched from reserving
one quarter of the available free memory to three quarters.  Apparently
this has some unfortunate side-affects for some workloads, and has
negatively effected chainloading[0] as well as Fedora CoreOS[1].

This patch changes it to reserve /half/ of available memory, in hopes
that this is a working compromise.

[0] https://bugzilla.redhat.com/show_bug.cgi?id=2115202
[1] coreos/fedora-coreos-tracker#1271

Signed-off-by: Peter Jones <pjones@redhat.com>

grub-core/kern/efi/mm.c

@@ -740,7 +740,7 @@ grub_efi_mm_init (void)
   /* By default, request three quarters of the available memory.  */
   total_pages = get_total_pages (filtered_memory_map, desc_size,
 				 filtered_memory_map_end);
-  required_pages = (total_pages >> 1) + (total_pages >> 2);
+  required_pages = (total_pages >> 1);
   if (required_pages < BYTES_TO_PAGES (MIN_HEAP_SIZE))
     required_pages = BYTES_TO_PAGES (MIN_HEAP_SIZE);
   else if (required_pages > BYTES_TO_PAGES (MAX_HEAP_SIZE))