qt4: fixed dependency on icu

qt4: fixed dependency on icu

Commit 46dcec6fd455584d9b5d0d7ff1e5b36fbe5a2d62 added 'icu' to DEPENDS
in qt4-x11 only, but enabled icu globally in qt4.inc.

This breaks build of qt4-embedded because this recipe does not have
such a DEPENDS but uses qt4.inc:

| icu.cpp:42:28: fatal error: unicode/utypes.h: No such file or directory
|  #include <unicode/utypes.h>
|                             ^
| compilation terminated.
| make: *** [icu.o] Error 1

Patch moves the 'icu' dependency into qt4.inc.

(From OE-Core rev: adb6e64d69fc947f2c8fa708dcbe854fd2b574f8)

Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Cc: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>