mesa: fix _NEW_PIXEL handling
10c75ae4 moved handling of this state to the functions that depend on ctx->_ImageTransferState.
We shouldn't clear the NEW_PIXEL bit in _mesa_update_state_locked or we might end up not applying a new state, eg:
glPixelTransferi(...) glClear(...) glTexSubImage2D(...) <-- won't use the new value set by glPixelTransferi because glClear caused _NEW_PIXEL to be cleared.
Fixes: 10c75ae4 ("mesa: move _mesa_update_pixel out of _mesa_update_state") Closes: #5273 (closed)