populate_sdk_ext: use SDK_CUSTOM_TEPLATECONF variable to enable custom templateconf.cfg
The current implementation will always pick an existing templateconf.cfg if
present else it will use the one from OE. A user might not always want to pick
an existing tempalteconf.cfg even if its present. Introduce
SDK_CUSTOM_TEMPLATECONF variable to provide an option for the user to specify if he
wants to use an existing custom templateconf.cfg or not
If SDK_CUSTOM_TEMPLATECONF=='1' then enable custom templateconf.cfg. By default
SDK_CUSTOM_TEMPLATECONF is set to '0'
Signed-off-by: Sai Hari Chandana Kalluri <chandana.kalluri@xilinx.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
