lib/crc: crc64: Add include/linux/crc64.h to kernel-api.rst

The other CRC functions with kerneldoc are here, so add crc64.h too.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250619183414.100082-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Author: Eric Biggers

Documentation/core-api/kernel-api.rst

@@ -156,6 +156,8 @@ CRC Functions
 
 .. kernel-doc:: include/linux/crc32.h
 
+.. kernel-doc:: include/linux/crc64.h
+
 Base 2 log and power Functions
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