Consolidate strmhz() implementation

ARM, i386, m68k and ppc all have identical implementations of strmhz().
Other architectures don't provide this function at all.

This patch moves strmhz() into lib_generic, reducing code duplication
and providing a more unified API across architectures.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
diff --git a/lib_generic/Makefile b/lib_generic/Makefile
index 4f6ce73..bf0e31d 100644
--- a/lib_generic/Makefile
+++ b/lib_generic/Makefile
@@ -40,6 +40,7 @@
 COBJS-y += sha1.o
 COBJS-$(CONFIG_SHA256) += sha256.o
 COBJS-y += string.o
+COBJS-y	+= strmhz.o
 COBJS-y += vsprintf.o
 COBJS-y += zlib.o