mesa: use _mesa_get_current_tex_object()

src/mesa/drivers/common/meta.c

                GLenum internalFormat, GLint x, GLint y,
                GLsizei width, GLsizei height, GLint border)
 {
-   struct gl_texture_unit *texUnit;
    struct gl_texture_object *texObj;
    struct gl_texture_image *texImage;
    GLsizei postConvWidth = width, postConvHeight = height;
    GLint bpp;
    void *buf;
 
-   texUnit = _mesa_get_current_tex_unit(ctx);
-   texObj = _mesa_select_tex_object(ctx, texUnit, target);
+   texObj = _mesa_get_current_tex_object(ctx, target);
    texImage = _mesa_get_tex_image(ctx, texObj, target, level);
 
    format = _mesa_base_tex_format(ctx, internalFormat);
                    GLint x, GLint y,
                    GLsizei width, GLsizei height)
 {
-   struct gl_texture_unit *texUnit;
    struct gl_texture_object *texObj;
    struct gl_texture_image *texImage;
    GLenum format, type;
    GLint bpp;
    void *buf;
 
-   texUnit = _mesa_get_current_tex_unit(ctx);
-   texObj = _mesa_select_tex_object(ctx, texUnit, target);
+   texObj = _mesa_get_current_tex_object(ctx, target);
    texImage = _mesa_select_tex_image(ctx, texObj, target, level);
 
    format = _mesa_get_format_base_format(texImage->TexFormat);