Fix some usage of removed private Skia functions & transitive dep

Attempting to fix broken roll.

sk_float_* functions map directly to <cmath> functions now, see
https://skia-review.googlesource.com/c/skia/+/842498

SkiaInterpolator requires <cstring> for memcpy. It seems this was
previously being pulled in through a transitive Skia inclusion which
is no longer present.

Bug: none
Change-Id: I155ead6c68eab066fb4d5588f35523aff2c4a050
Test: builds
Flag: EXEMPT build fix
diff --git a/libs/hwui/SkiaInterpolator.cpp b/libs/hwui/SkiaInterpolator.cpp
index c67b135..5a45ad9 100644
--- a/libs/hwui/SkiaInterpolator.cpp
+++ b/libs/hwui/SkiaInterpolator.cpp
@@ -20,6 +20,7 @@
 #include "include/core/SkTypes.h"
 
 #include <cstdlib>
+#include <cstring>
 #include <log/log.h>
 
 typedef int Dot14;