staging: sm750fb: drop redundant defines for PLL_CTRL fields

The PLL_CTRL fields have common defines for several PLL control
registers and re-defining the same values per register is not needed.

Signed-off-by: Mike Rapoport <mike.rapoport@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>