libomxil_xlnx: Use more appropriate header file path variable name
libomxil_xlnx: Use more appropriate header file path variable name

Updating the variable name used for header files in this recipe as
the makefile used for compilation of this package(libomxil-xlnx)
has been updated to use more appropriate name "EXTERNAL_INCLUDE"
to point to VCU control software headers.

Signed-off-by: Devarsh Thakkar <d28a6403f1a99a1f0c8c3d3528f3fec7766762f8@xilinx.com>
Signed-off-by: Manjukumar Matha <4c64a17569570cb9f1048973bce031c402b55312@xilinx.com>

Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux,Xilinx/meta-petalinux