Add missing "const" to SkMD5::finish::PADDING
Add missing "const" to SkMD5::finish::PADDING

This moves it from .data to .rodata ELF section (more efficient)

Bug: chromium:747064
Change-Id: I4d12ce6622bd9d1264d46e48855a43f00671bee4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/268200
Auto-Submit: Andrew Grieve <f5a68dd3fb158cd420e05ca279f52a686c662bee@chromium.org>
Commit-Queue: Mike Klein <14574f09dfa9b4e14759b88c3426a495a0e627b0@google.com>
Reviewed-by: Mike Klein <14574f09dfa9b4e14759b88c3426a495a0e627b0@google.com>

google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia