Fix indentation for PowerPC ReleaseNotes

Author: Ahsan Saghir

llvm/docs/ReleaseNotes.rst

@@ -178,24 +178,33 @@ Optimization:
 Codegen:
 
 * POWER10 support
-* Added PC Relative addressing
-* Added __int128 vector bool support
+
+  * Added PC Relative addressing
+  * Added __int128 vector bool support
+
 * Security enhancement via probe-stack attribute support to protect against stack clash
 * Floating point support enhancements
-* Improved half precision and quad precision support, including GLIBC
-* constrained FP operation support for arithmetic/rounding/max/min
-* cleaning up fast math flags checks in DAGCombine, Legalizer, and Lowering
+
+  * Improved half precision and quad precision support, including GLIBC
+  * constrained FP operation support for arithmetic/rounding/max/min
+  * cleaning up fast math flags checks in DAGCombine, Legalizer, and Lowering
+
 * Performance improvements from instruction exploitation, especially for vector permute on LE
 * Scheduling enhancements
-* Added MacroFusion for POWER8
-* Added post-ra heuristics for POWER9
+
+  * Added MacroFusion for POWER8
+  * Added post-ra heuristics for POWER9
+
 * Target dependent passes tuning
-* Updated LoopStrengthReduce to use instruction number as first priority
-* Enhanced MachineCombiner to expose more ILP
+
+  * Updated LoopStrengthReduce to use instruction number as first priority
+  * Enhanced MachineCombiner to expose more ILP
+
 * Code quality and maintenance enhancements
-* Enabled more machine verification passes
-* Added ability to parse and emit additional extended mnemonics
-* Numerous bug fixes
+
+  * Enabled more machine verification passes
+  * Added ability to parse and emit additional extended mnemonics
+  * Numerous bug fixes
 
 AIX Support Improvements: