RFA: asm-source.exp: use switch instead of if chain

[Jim Blandy]

I've committed this.

Jim Blandy <jimb@redhat.com> writes:
> This isn't intended to have any effect on behavior, but it seems a
> little more legible to me.
> 
> 2003-04-28  Jim Blandy  <jimb@redhat.com>
> 
> 	* gdb.asm/asm-source.exp: Use a 'switch -glob' statement, not a
> 	succession of 'if' statements.