module.bbclass: add KBUILD_EXTRA_SYMBOLS to install

module.bbclass: add KBUILD_EXTRA_SYMBOLS to install

Symbols are used during install as well, adding KBUILD_EXTRA_SYMBOLS enables
successful installation.

    | DEBUG: Executing shell function do_install
    | NOTE: make -j 22 KERNEL_SRC=xxx/kernel-source -C xxx/drivers
    KDIR=xxx/kernel-source DEPMOD=echo
    MODLIB=xxx/image/lib/modules/6.6.75-yocto-standard-00189-g530c419bc9db
    INSTALL_FW_PATH=xxx/image/lib/firmware CC=aarch64-poky-linux-gcc
    -fuse-ld=bfd -fcanon-prefix-map  LD=aarch64-poky-linux-ld.bfd
    OBJCOPY=aarch64-poky-linux-objcopy  STRIP=aarch64-poky-linux-strip
    O=xxx/kernel-build-artifacts modules_install
    | make: Entering directory 'xxx/drivers'
    | make -C xxx/kernel-source M=xxx/drivers modules
    | make[1]: Entering directory 'xxx/kernel-source'
    | make[2]: Entering directory 'xxx/kernel-build-artifacts'
    |   MODPOST xxx/drivers/Module.symvers
    | ERROR: modpost: "xxx" [xxx/xxx.ko] undefined!

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>