[MIPS] SEAD defconfig build fix

Signed-off-by: Maciej W. Rozycki <macro@mips.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Makefile

@@ -330,6 +330,7 @@ load-$(CONFIG_MIPS_MALTA)	+= 0xffffffff80100000
 # MIPS SEAD board
 #
 core-$(CONFIG_MIPS_SEAD)	+= arch/mips/mips-boards/sead/
+cflags-$(CONFIG_MIPS_SEAD)	+= -Iinclude/asm-mips/mach-mips
 load-$(CONFIG_MIPS_SEAD)	+= 0xffffffff80100000
 
 #