Samsung fixes for v5.19

Both fixes are for issues present before v5.19 merge window:
1. Correct UART clocks on Exynos7885.  Although the initial, fixed
   DTS commit is from v5.18, the issue will be exposed with a upcoming fix
   to Exynos7885 clock driver, so we need to correct the DTS earlier.
2. Fix theoretical OF node leak in Exynos machine code.