efi_loader: new function utf8_to_utf16

Provide a conversion function from utf8 to utf16.

Add missing #include <linux/types.h> in include/charset.h.
Remove superfluous #include <common.h> in lib/charset.c.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/include/charset.h b/include/charset.h
index 37a3278..2662c2f 100644
--- a/include/charset.h
+++ b/include/charset.h
@@ -9,6 +9,8 @@
 #ifndef __CHARSET_H_
 #define __CHARSET_H_
 
+#include <linux/types.h>
+
 #define MAX_UTF8_PER_UTF16 3
 
 /**
@@ -62,4 +64,17 @@
  */
 uint8_t *utf16_to_utf8(uint8_t *dest, const uint16_t *src, size_t size);
 
+/**
+ * utf8_to_utf16() - Convert an utf8 string to utf16
+ *
+ * Converts up to 'size' characters of the utf16 string 'src' to utf8
+ * written to the 'dest' buffer. Stops at 0x00.
+ *
+ * @dest   the destination buffer to write the utf8 characters
+ * @src    the source utf16 string
+ * @size   maximum number of utf16 characters to convert
+ * @return the pointer to the first unwritten byte in 'dest'
+ */
+uint16_t *utf8_to_utf16(uint16_t *dest, const uint8_t *src, size_t size);
+
 #endif /* __CHARSET_H_ */