doc: improve uefi::boot::memory_map() documentation

Author: phip1611

uefi/src/boot.rs

@@ -248,8 +248,10 @@ pub(crate) fn memory_map_size() -> MemoryMapMeta {
 /// and returns a [`MemoryMapOwned`]. 
 /// 
 /// The implementation tries to mitigate some UEFI pitfalls, such as getting
-/// the right allocation size for the memory map. Therefore, a return value of 
-/// [`Status::BUFFER_TOO_SMALL`] should be treated as unrecoverable error.
+/// the right allocation size for the memory map to prevent
+/// [`Status::BUFFER_TOO_SMALL`]. If [`Status::BUFFER_TOO_SMALL`] is returned, 
+/// further calls are likely to fail as well. If so, the situation may be
+/// considered as unrecoverable error.
 ///
 /// # Parameters
 ///