powerpc/mpc85xx: Avoid hardcoding in SPL linker script

SPL linker has fix location of bootpg and reset vector with respect to text base.
It is not necessary to have fixed locations.

Avoid such hardcoding.

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

arch/powerpc/cpu/mpc85xx/u-boot-spl.lds

@@ -66,11 +66,16 @@ SECTIONS
 	} :text = 0xffff
 #else
 #if defined(CONFIG_FSL_IFC) /* Restrict bootpg at 4K boundry for IFC */
-	.bootpg ADDR(.text) + 0x1000 :
+#ifndef BOOT_PAGE_OFFSET
+#define BOOT_PAGE_OFFSET 0x1000
+#endif
+	.bootpg ADDR(.text) + BOOT_PAGE_OFFSET :
 	{
 		arch/powerpc/cpu/mpc85xx/start.o (.bootpg)
 	}
+#ifndef RESET_VECTOR_OFFSET
 #define RESET_VECTOR_OFFSET 0x1ffc /* IFC has 8K sram */
+#endif
 #elif defined(CONFIG_FSL_ELBC)
 #define RESET_VECTOR_OFFSET 0xffc /* LBC has 4k sram */
 #else