[clang][SveEmitter] Fix enum declarations. [NFCI]

Adapt the declarations of `svpattern` and `svprfop` to the most recent
one defined in section "5. Enum declarations" of the SVE ACLE
specifications [1].

The signature of the intrinsics using these enums have been changed
accordingly.

A test has been added to make sure that `svpattern` and `svprfop` are
not typedefs.

[1] https://developer.arm.com/documentation/100987/latest, version
00bet6

Reviewed By: joechrisellis

Differential Revision: https://reviews.llvm.org/D91333