glsl: Minor cleanups after previous commit

glsl: Minor cleanups after previous commit

I think it's more clear to only call emit_access once.  The only
difference between the two calls is the value of size_mul used for the
offset parameter... but you really have to look at it to be sure.

The s/is_64bit/is_double/ change is because there are no int64_t or
uint64_t matrix types.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Thomas Helland <thomashelland90@gmail.com>