The error_emitted flag is used in semantic checking to prevent spurious
cascading errors.  For example,

void foo(sampler2D s, float a)
{
    float x = a + (1.2 + s);

    ...
}

should only generate a single error.  Without the error_emitted flag for
the first error, "a + ..." would also generate an error.

However, a bunch of cases in _mesa_ast_array_index_to_hir that were
setting error_emitted would mask legitimate errors.  For example,

    vec4 a[7];
    float b = a[3.14];

should generate two error (float index and type mismatch in assignment).
The uses of error_emitted would cause only the first to be emitted.

This patch removes most of the places in _mesa_ast_array_index_to_hir
that would set the error_emitted flag.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>