fbdev: aty128fb: replace PPC_OF with PPC

The PPC_OF is a ppc specific option which is used to mean that the
firmware device tree access functions are available. Since all the
ppc platforms have a device tree, it is aways set to 'y' for ppc.
So it makes no sense to keep a such option in the current kernel.
Replace it with PPC.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/video/fbdev/aty/aty128fb.c

@@ -965,7 +965,7 @@ static void __iomem *aty128_find_mem_vbios(struct aty128fb_par *par)
 /* fill in known card constants if pll_block is not available */
 static void aty128_timings(struct aty128fb_par *par)
 {
-#ifdef CONFIG_PPC_OF
+#ifdef CONFIG_PPC
 	/* instead of a table lookup, assume OF has properly
 	 * setup the PLL registers and use their values
 	 * to set the XCLK values and reference divider values */
@@ -979,7 +979,7 @@ static void aty128_timings(struct aty128fb_par *par)
 	if (!par->constants.ref_clk)
 		par->constants.ref_clk = 2950;
 
-#ifdef CONFIG_PPC_OF
+#ifdef CONFIG_PPC
 	x_mpll_ref_fb_div = aty_ld_pll(X_MPLL_REF_FB_DIV);
 	xclk_cntl = aty_ld_pll(XCLK_CNTL) & 0x7;
 	Nx = (x_mpll_ref_fb_div & 0x00ff00) >> 8;