powerpc: P1024RDB: Separate from P1_P2_RDB_PC in Kconfig

Use TARGET_P1024RDB instead of sharing with TARGET_P1_P2_RDB_PC to
simplify Kconfig and macros.

Remove macro CONFIG_P1024RDB.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/P1024RDB_SPIFLASH_defconfig b/configs/P1024RDB_SPIFLASH_defconfig
index 837b069..94c45c0 100644
--- a/configs/P1024RDB_SPIFLASH_defconfig
+++ b/configs/P1024RDB_SPIFLASH_defconfig
@@ -7,12 +7,12 @@
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
 CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_P1_P2_RDB_PC=y
+CONFIG_TARGET_P1024RDB=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="P1024RDB,SPIFLASH"
+CONFIG_SYS_EXTRA_OPTIONS="SPIFLASH"
 CONFIG_BOOTDELAY=10
 CONFIG_SPL=y
 CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y