kconfig: prepend CT-NG's version tag to PKGVERSION

"crosstool-NG-${CT_VERSION}" is currently the default for TOOLCHAIN_PKGVERSION,
and this options is passed as is to --with-pkgversion.

This patch prepends "crosstool-NG ${CT_VERSION}" to TOOLCHAIN_PKGVERSION before
passing it to --with-pkgversion.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

 # Blackfin specific configuration file

 ## select ARCH_SUPPORTS_32

 ## select ARCH_DEFAULT_32

 ## select ARCH_DEFAULT_LE

 ## select ARCH_SUPPORT_ARCH

 ## select ARCH_SUPPORT_CPU

 ## select ARCH_SUPPORT_TUNE

 ## select ARCH_SUPPORT_FPU

 ##

 ## help The Blackfin architecture