selftests/powerpc: Update the stack expansion test

Update the stack expansion load/store test to take into account the
new allowance of 4224 bytes below the stack pointer.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200724092528.1578671-3-mpe@ellerman.id.au

tools/testing/selftests/powerpc/mm/stack_expansion_ldst.c

@@ -186,17 +186,17 @@ static void test_one_type(enum access_type type, unsigned long page_size, unsign
 	// But if we go past the rlimit it should fail
 	assert(test_one(DEFAULT_SIZE, rlim_cur + 1, type) != 0);
 
-	// Above 1MB powerpc only allows accesses within 2048 bytes of
+	// Above 1MB powerpc only allows accesses within 4224 bytes of
 	// r1 for accesses that aren't stdu
-	assert(test_one(1 * _MB + page_size - 128, -2048, type) == 0);
+	assert(test_one(1 * _MB + page_size - 128, -4224, type) == 0);
 #ifdef __powerpc__
-	assert(test_one(1 * _MB + page_size - 128, -2049, type) != 0);
+	assert(test_one(1 * _MB + page_size - 128, -4225, type) != 0);
 #else
-	assert(test_one(1 * _MB + page_size - 128, -2049, type) == 0);
+	assert(test_one(1 * _MB + page_size - 128, -4225, type) == 0);
 #endif
 
 	// By consuming 2MB of stack we test the stdu case
-	assert(test_one(2 * _MB + page_size - 128, -2048, type) == 0);
+	assert(test_one(2 * _MB + page_size - 128, -4224, type) == 0);
 }
 
 static int test(void)