ppc: qemu: Drop fixed_sdram()

This function is not called anywhere. Only fsl_ddr_sdram_size() is
necessary [1] for QEMU. Drop it.

[1] arch/powerpc/cpu/mpc85xx/cpu.c::dram_init()

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

board/freescale/qemu-ppce500/qemu-ppce500.c

@@ -187,11 +187,6 @@ static uint64_t get_linear_ram_size(void)
 	panic("Couldn't determine RAM size");
 }
 
-phys_size_t fixed_sdram(void)
-{
-	return get_linear_ram_size();
-}
-
 phys_size_t fsl_ddr_sdram_size(void)
 {
 	return get_linear_ram_size();