sha512.c: Grammar Fixes and Spell Checks in Implementation Notes

Added commas for sentence openers in Implementation Notes. Fixed
spelling of "reasons" section of the notes.

CLA: trivial

Co-authored-by: Tom Cosgrove <tom.cosgrove@arm.com>

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #24241)

crypto/sha/sha512.c

@@ -18,16 +18,16 @@
 /*-
  * IMPLEMENTATION NOTES.
  *
- * As you might have noticed 32-bit hash algorithms:
+ * As you might have noticed, 32-bit hash algorithms:
  *
  * - permit SHA_LONG to be wider than 32-bit
  * - optimized versions implement two transform functions: one operating
- *   on [aligned] data in host byte order and one - on data in input
+ *   on [aligned] data in host byte order, and one operating on data in input
  *   stream byte order;
  * - share common byte-order neutral collector and padding function
  *   implementations, crypto/md32_common.h;
  *
- * Neither of the above applies to this SHA-512 implementations. Reasons
+ * Neither of the above applies to this SHA-512 implementation. Reasons
  * [in reverse order] are:
  *
  * - it's the only 64-bit hash algorithm for the moment of this writing,