service/ldr: Amend layout of the NRO header

The first word is just a padding byte, it's not an actual entry
instruction. Also renames the rest of the entries according to
SwitchBrew.

src/core/hle/service/ldr/ldr.cpp

@@ -414,13 +414,13 @@ private:
     using SHA256Hash = std::array<u8, 0x20>;
 
     struct NROHeader {
-        u32_le entrypoint_insn;
+        INSERT_PADDING_WORDS(1);
         u32_le mod_offset;
         INSERT_PADDING_WORDS(2);
         u32_le magic;
-        INSERT_PADDING_WORDS(1);
+        u32_le version;
         u32_le nro_size;
-        INSERT_PADDING_WORDS(1);
+        u32_le flags;
         u32_le text_offset;
         u32_le text_size;
         u32_le ro_offset;