selftest/x86: build both bitnesses

Using uname with the processor flag option in some cases can yield 'unknown'
so lets use the machine flag option as it is deterministic. Add a dependency
for all_32 when building on a x86 64 bit host so that both bitnesses are
built in this case.

Cc: Andy Lutomirski <luto@amacapital.net>
Acked-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Tyler Baker <tyler.baker@linaro.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/x86/Makefile

@@ -7,13 +7,13 @@ BINARIES_64 := $(TARGETS_C_BOTHBITS:%=%_64)
 
 CFLAGS := -O2 -g -std=gnu99 -pthread -Wall
 
-UNAME_P := $(shell uname -p)
+UNAME_M := $(shell uname -m)
 
 # Always build 32-bit tests
 all: all_32
 
 # If we're on a 64-bit host, build 64-bit tests as well
-ifeq ($(shell uname -p),x86_64)
+ifeq ($(UNAME_M),x86_64)
 all: all_64
 endif