libtomcrypt: fix build without wchar

libtomcrypt: fix build without wchar

GCC defines wchar_t even when wchar support is disabled in uClibc. The
LTC_NO_WCHAR macro triggers a local definition of wchar_t that conflicts
with the GCC defined one. Remove LTC_NO_WCHAR to avoid that.

See also https://github.com/libtom/libtomcrypt/issues/313 for more
discussion about this.

Fixes:
http://autobuild.buildroot.net/results/4ff/4ffb593185f7520d2d9a9cc988aa9c510f253930/

Cc: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>