pvmfw: fix bug in getting pvmfw config entry

Because of wrong usage of unsafe function (slice::from_raw_parts_mut),
it causes appending tailing zeros for each pvmfw config entry.

Bug: 285855885
Test: Presubmit
Change-Id: I5022a09abb9152d77a148cabfe3168c0f78bae15
diff --git a/pvmfw/src/config.rs b/pvmfw/src/config.rs
index 7023b95..4957df2 100644
--- a/pvmfw/src/config.rs
+++ b/pvmfw/src/config.rs
@@ -288,6 +288,6 @@
 
     unsafe fn from_raw_range_mut(ptr: usize, range: NonEmptyRange) -> &'a mut [u8] {
         // SAFETY: The caller must ensure that the range is valid from ptr.
-        unsafe { slice::from_raw_parts_mut((ptr + range.start) as *mut u8, range.end()) }
+        unsafe { slice::from_raw_parts_mut((ptr + range.start) as *mut u8, range.len()) }
     }
 }