HS 2.0: Fix hs20_spp_server compile error

Need to add a new -I path to get it to compile.

Signed-off-by: Ben Greear <greearb@candelatech.com>

hs20/server/Makefile

@@ -12,6 +12,7 @@ ifndef CFLAGS
 CFLAGS = -MMD -O2 -Wall -g
 endif
 
+CFLAGS += -I../../src
 CFLAGS += -I../../src/utils
 CFLAGS += -I../../src/crypto