arch: arm: Fix SZ_64K undeclared compilation error

Macro SZ_64K is undeclared. Include sizes.h to fix the compilation
error.
Signed-off-by: NWasim Khan <wasim.khan@nxp.com>
Reviewed-by: NTom Rini <trini@konsulko.com>

arch/arm/lib/gic-v3-its.c

@@ -6,6 +6,7 @@
 #include <asm/gic.h>
 #include <asm/gic-v3.h>
 #include <asm/io.h>
+#include <linux/sizes.h>
 
 static u32 lpi_id_bits;