powerpc/t4240qds: Move SoC define into boards.cfg

Separate CONFIG_PPC_T4240 from board config file. Prepare to add more SoC
variants supported on the same board.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
diff --git a/boards.cfg b/boards.cfg
index 5d78064..27815c6 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -893,9 +893,9 @@
 stxgp3                       powerpc     mpc85xx     stxgp3              stx
 stxssa                       powerpc     mpc85xx     stxssa              stx            -           stxssa
 stxssa_4M                    powerpc     mpc85xx     stxssa              stx            -           stxssa:STXSSA_4M
-T4240QDS                     powerpc     mpc85xx     t4qds               freescale
-T4240QDS_SDCARD              powerpc     mpc85xx     t4qds               freescale	-           T4240QDS:RAMBOOT_PBL,SDCARD,SYS_TEXT_BASE=0xFFF80000
-T4240QDS_SPIFLASH            powerpc     mpc85xx     t4qds               freescale	-           T4240QDS:RAMBOOT_PBL,SPIFLASH,SYS_TEXT_BASE=0xFFF80000
+T4240QDS                     powerpc     mpc85xx     t4qds               freescale      -           T4240QDS:PPC_T4240
+T4240QDS_SDCARD              powerpc     mpc85xx     t4qds               freescale	-           T4240QDS:PPC_T4240,RAMBOOT_PBL,SDCARD,SYS_TEXT_BASE=0xFFF80000
+T4240QDS_SPIFLASH            powerpc     mpc85xx     t4qds               freescale	-           T4240QDS:PPC_T4240,RAMBOOT_PBL,SPIFLASH,SYS_TEXT_BASE=0xFFF80000
 B4860QDS                     powerpc     mpc85xx     b4860qds            freescale      -           B4860QDS:PPC_B4860
 B4860QDS_NAND		     powerpc     mpc85xx     b4860qds            freescale      -           B4860QDS:PPC_B4860,RAMBOOT_PBL,NAND,SYS_TEXT_BASE=0xFFF80000
 B4860QDS_SPIFLASH            powerpc     mpc85xx     b4860qds            freescale	-           B4860QDS:PPC_B4860,RAMBOOT_PBL,SPIFLASH,SYS_TEXT_BASE=0xFFF80000