While parsing the nm output, we need to account for the fact that 64-bit kernels
have 64-bit wide addresses. While at it, replace the grep | sed combo with a
single awk invocation and a stronger regex.
Fixes: 2ef0acc5fc "kernel-build: fix
STRIP_KERNEL_EXPORTS for recent kernels"
Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>