cmd/internal/obj/arm64: fix typos in document
cmd/internal/obj/arm64: fix typos in document

Correct "PCALING" to "PCALIGN".

Change-Id: Id80728142febd2a42e112dc06a6c1bc0759687e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/232697
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/go,golang/go,CAFxX/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,golang/go,cloudflare/go,cloudflare/go,akutz/go,golang/go,CAFxX/go,akutz/go,akutz/go,nawawi/go,CAFxX/go,akutz/go,golang/go,cloudflare/go,cloudflare/go,nawawi/go,akutz/go,CAFxX/go,CAFxX/go,cloudflare/go,cloudflare/go,nawawi/go,nawawi/go,akutz/go,akutz/go,CAFxX/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,CAFxX/go,golang/go,cloudflare/go,akutz/go