mesa: Pack gl_program_parameter struct

The gl_register_file doesn't need 16 bits, so shorten it and use the
extra room for 'Padded' (also mark it as a single bit).  This shrinks
the struct size from 32 bytes to 24 bytes.

See also 4794fbc86e ("mesa: reduce the size of gl_program_parameter")
that shrinked from 40 to 24 and later 7536af670b ("glsl: fix shader
cache for packed param list") that added `Padded`.

v2: Use just 5 bits for gl_register_file.  (Timothy)

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>

src/mesa/program/prog_parameter.h

@@ -91,8 +91,16 @@ typedef union gl_constant_value
 struct gl_program_parameter
 {
    const char *Name;        /**< Null-terminated string */
-   gl_register_file Type:16;  /**< PROGRAM_CONSTANT or STATE_VAR */
+   gl_register_file Type:5;  /**< PROGRAM_CONSTANT or STATE_VAR */
+
+   /**
+    * We need to keep track of whether the param is padded for use in the
+    * shader cache.
+    */
+   bool Padded:1;
+
    GLenum16 DataType;         /**< GL_FLOAT, GL_FLOAT_VEC2, etc */
+
    /**
     * Number of components (1..4), or more.
     * If the number of components is greater than 4,
@@ -104,12 +112,6 @@ struct gl_program_parameter
     * A sequence of STATE_* tokens and integers to identify GL state.
     */
    gl_state_index16 StateIndexes[STATE_LENGTH];
-
-   /**
-    * We need to keep track of whether the param is padded for use in the
-    * shader cache.
-    */
-   bool Padded;
 };