lib: add some utf16 handling helpers

We'll eventually want these in a few places in efi_loader, and also
vsprintf.

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/lib/Makefile b/lib/Makefile
index da6a11a..15bba9e 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -18,6 +18,7 @@
 obj-$(CONFIG_CMD_DHRYSTONE) += dhry/
 
 obj-$(CONFIG_AES) += aes.o
+obj-y += charset.o
 obj-$(CONFIG_USB_TTY) += circbuf.o
 obj-y += crc7.o
 obj-y += crc8.o