x86: Factor out common values in the link script

Define the reset base in config.mk so that it does not need to be calculated
twice in the link script. Also tidy up the START_16 and RESET_VEC_LOC values
to fit with this new approach.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/config.mk

@@ -12,5 +12,6 @@ PLATFORM_CPPFLAGS += -D__I386__ -Werror
 # DO NOT MODIFY THE FOLLOWING UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!
 LDPPFLAGS += -DRESET_SEG_START=0xffff0000
 LDPPFLAGS += -DRESET_SEG_SIZE=0x10000
-LDPPFLAGS += -DRESET_VEC_LOC=0xfff0
-LDPPFLAGS += -DSTART_16=0xf800
+LDPPFLAGS += -DRESET_VEC_LOC=0xfffffff0
+LDPPFLAGS += -DSTART_16=$(CONFIG_SYS_X86_START16)
+LDPPFLAGS += -DRESET_BASE="CONFIG_SYS_TEXT_BASE + (CONFIG_SYS_MONITOR_LEN - RESET_SEG_SIZE)"

arch/x86/cpu/u-boot.lds

@@ -66,15 +66,19 @@ SECTIONS
 	/DISCARD/ : { *(.gnu*) }
 
 #ifdef CONFIG_X86_RESET_VECTOR
-
 	/*
 	 * The following expressions place the 16-bit Real-Mode code and
 	 * Reset Vector at the end of the Flash ROM
 	 */
-	. = START_16;
-	.start16 : AT (CONFIG_SYS_TEXT_BASE + (CONFIG_SYS_MONITOR_LEN - RESET_SEG_SIZE + START_16)) { KEEP(*(.start16)); }
+	. = START_16 - RESET_SEG_START;
+	.start16 : AT (START_16) {
+		KEEP(*(.start16));
+	}
 
-	. = RESET_VEC_LOC;
-	.resetvec : AT (CONFIG_SYS_TEXT_BASE + (CONFIG_SYS_MONITOR_LEN - RESET_SEG_SIZE + RESET_VEC_LOC)) { KEEP(*(.resetvec)); }
+	. = RESET_VEC_LOC - RESET_SEG_START;
+	.resetvec : AT (RESET_VEC_LOC) {
+		KEEP(*(.resetvec));
+	}
 #endif
+
 }