nir: Use _mesa_flsll(InputsRead) in prog->nir.

InputsRead is a 64-bit bitfield.  Using _mesa_fls would silently
truncate off the high bits, claiming inputs 32..56 (VARYING_SLOT_MAX)
were never read.

Using <= here was a hack I threw in at the last minute to fix programs
which happened to use input slot 32.  Switch back to using < now that
the underlying problem is fixed.

Fixes crashes in "Euro Truck Simulator 2" when using prog->nir, which
uses input slot 33.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/mesa/program/prog_to_nir.c

@@ -931,8 +931,8 @@ setup_registers_and_variables(struct ptn_compile *c)
    struct nir_shader *shader = b->shader;
 
    /* Create input variables. */
-   const int last_input = _mesa_fls(c->prog->InputsRead);
-   for (int i = 0; i <= last_input; i++) {
+   const int num_inputs = _mesa_flsll(c->prog->InputsRead);
+   for (int i = 0; i < num_inputs; i++) {
       if (!(c->prog->InputsRead & BITFIELD64_BIT(i)))
          continue;
       nir_variable *var = rzalloc(shader, nir_variable);