fix(m68k): correct SR register read (#2161)

The SR register in the `CPUM68KState` struct does not contain the value
of the lower 5 flags. To compute them, we must OR the CCR values with
the SR register to get the true SR value.

tests/unit/test_m68k.c

@@ -37,4 +37,29 @@ static void test_move_to_sr(void)
     OK(uc_close(uc));
 }
 
-TEST_LIST = {{"test_move_to_sr", test_move_to_sr}, {NULL, NULL}};
+static void test_sr_contains_flags(void)
+{
+    uc_engine *uc;
+    uint8_t code[] = {
+        0x76, 0xed, // moveq #-19, %d3
+    };
+
+    uint32_t d3, sr;
+
+    uc_common_setup(&uc, UC_ARCH_M68K, UC_MODE_BIG_ENDIAN, code, sizeof(code),
+                    UC_CPU_M68K_M68000);
+
+    OK(uc_emu_start(uc, code_start, code_start + sizeof(code), 0, 0));
+
+    OK(uc_reg_read(uc, UC_M68K_REG_D3, &d3));
+    OK(uc_reg_read(uc, UC_M68K_REG_SR, &sr));
+
+    TEST_CHECK(d3 == 0xFFFFFFED);
+    TEST_CHECK((sr & 0x8) /* N flag */ == 0x8);
+
+    OK(uc_close(uc));
+}
+
+TEST_LIST = {{"test_move_to_sr", test_move_to_sr},
+             {"test_sr_contains_flags", test_sr_contains_flags},
+             {NULL, NULL}};