systemd-boot.bbclass: Fix SYSYTEMD_BOOT_CFG creation

This patch makes sure the directory which will contain
the systemd configuration (loader.conf) is created before
the configuration file is written, fixing errors when it
tried to write it to a non-existent directory

(From OE-Core rev: f4ba23212c97fb8c3351a3cf981ee355ae2fc9b1)

Signed-off-by: Alejandro Hernandez <alejandro.hernandez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/systemd-boot.bbclass

@@ -72,6 +72,9 @@ python build_efi_cfg() {
         return
 
     cfile = d.getVar('SYSTEMD_BOOT_CFG')
+    cdir = os.path.dirname(cfile)
+    if not os.path.exists(cdir):
+        os.makedirs(cdir)
     try:
          cfgfile = open(cfile, 'w')
     except OSError: