systemd: Fix musl fix patch

Current patch with fail when stdint.h is in include path before this
typedef which can also happen with re-includes. Therefore shunt that
by defining __DEFINED_wchar_t which helps musl builds of systemd-boot
recipe

(From OE-Core rev: 7fce95e47601f766b384bc0d5805986ad933681f)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/systemd/systemd/0004-src-boot-efi-efi-string.c-define-wchar_t-from-__WCHA.patch

@@ -21,17 +21,16 @@ Signed-off-by: Alexander Kanavin <alex@linutronix.de>
  src/boot/efi/efi-string.c | 5 +++++
  1 file changed, 5 insertions(+)
 
-diff --git a/src/boot/efi/efi-string.c b/src/boot/efi/efi-string.c
-index 22923d60f6..22a8d1ef71 100644
 --- a/src/boot/efi/efi-string.c
 +++ b/src/boot/efi/efi-string.c
-@@ -2,7 +2,12 @@
+@@ -2,7 +2,13 @@
  
  #include <stdbool.h>
  #include <stdint.h>
 +
 +#if SD_BOOT
 +typedef __WCHAR_TYPE__ wchar_t;
++#define __DEFINED_wchar_t
 +#else
  #include <wchar.h>
 +#endif