[gas][aarch64] Turn on SVE when using f32mm or f64mm extensions

[gas][aarch64] Turn on SVE when using f32mm or f64mm extensions

There are no instructions under these matrix multiply extensions that
can be used without having SVE enabled.
Since these extensions require SVE, we make that explicit in the options
table.

Tested on aarch64-none-elf without regressions.

gas/ChangeLog:

2020-01-13  Matthew Malcomson  <matthew.malcomson@arm.com>

	* config/tc-aarch64.c (f64mm, f32mm): Add sve as a feature
	dependency.