[rust][inspect] Make fields of *HistogramParams public

TESTED=fx run-test fuchsia_inspect_tests

Change-Id: Ibf9c357cd397fec3eb95fcbedab997658bb3b377
diff --git a/garnet/public/rust/fuchsia-inspect/src/lib.rs b/garnet/public/rust/fuchsia-inspect/src/lib.rs
index 6c3b9f2..6eb85f8 100644
--- a/garnet/public/rust/fuchsia-inspect/src/lib.rs
+++ b/garnet/public/rust/fuchsia-inspect/src/lib.rs
@@ -271,9 +271,9 @@
 }
 
 pub struct LinearHistogramParams<T> {
-    floor: T,
-    step_size: T,
-    buckets: u8,
+    pub floor: T,
+    pub step_size: T,
+    pub buckets: u8,
 }
 
 /// Utility for generating functions to create a linear histogram property.
@@ -302,10 +302,10 @@
 }
 
 pub struct ExponentialHistogramParams<T> {
-    floor: T,
-    initial_step: T,
-    step_multiplier: T,
-    buckets: u8,
+    pub floor: T,
+    pub initial_step: T,
+    pub step_multiplier: T,
+    pub buckets: u8,
 }
 
 /// Utility for generating functions to create an exponential histogram property.