lib: Remove the BOOTBLOCK_CUSTOM compile guard

This CL allows that everyone can use main() in lib/bootblock.c
even if you select CONFIG_BOOTBLOCK_CUSTOM. I also rename main
functions used in some soc/ to avoid the collision with the
main function defined at lib/bootblock.c.

Change-Id: I0575c9d1ce9dea9facfcc86760dff4deee9c1e29
Signed-off-by: Asami Doi <d0iasm.pub@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34250
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/mips/bootblock.S

@@ -33,7 +33,7 @@ _start:
 	addi	$t0, $t0, 4
 
 	/* Run main */
-	b	main
+	b	mips_main
 
 	/*
 	 * Should never return from main. Make sure there is no branch in the

src/arch/mips/bootblock_simple.c

@@ -19,7 +19,10 @@
 #include <halt.h>
 #include <program_loading.h>
 
-void main(void)
+/* called from assembly in bootblock.S */
+void mips_main(void);
+
+void mips_main(void)
 {
 	bootblock_cpu_init();