disk: Rename grub_disk_get_size() to grub_disk_native_sectors()

The function grub_disk_get_size() is confusingly named because it actually
returns a sector count where the sectors are sized in the GRUB native sector
size. Rename to something more appropriate.

Suggested-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Patrick Steinhardt <ps@pks.im>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/disk/efi/efidisk.c

@@ -867,7 +867,7 @@ grub_efidisk_get_device_name (grub_efi_handle_t *handle)
       if (ctx.hd->partition_start == 0
 	  && (ctx.hd->partition_size << (parent->log_sector_size
 					 - GRUB_DISK_SECTOR_BITS))
-	  == grub_disk_get_size (parent))
+	  == grub_disk_native_sectors (parent))
 	{
 	  dev_name = grub_strdup (parent->name);
 	}