sreset_world: re-enable the non-stb build

This breaks the test when you don't have the SKIBOOT_ENABLE_MAMBO_STB
flag set, as the binary is removed as an intermediate artefact (I
suspect) when building the sreset_world.stb binary.

Fixes: 1ddf7e5 ("Mambo: run hello_world and sreset_world tests with Secure and Trusted Boot")
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

test/sreset_world/Makefile.check

@@ -1,4 +1,4 @@
-SRESET_WORLD_TEST := test/sreset_world/sreset_kernel/sreset_kernel.stb
+SRESET_WORLD_TEST := test/sreset_world/sreset_kernel/sreset_kernel
 SRESET_WORLD_STB_TEST := test/sreset_world/sreset_kernel/sreset_kernel.stb
 
 .PHONY: sreset_world-tests