ipq40xx: speed up ath10k-caldata extraction

ipq40xx: speed up ath10k-caldata extraction

Reading and writing to and from flash storage is slow and currently,
the ath10kcal_extract() scripts are even more at an disadvantage
because they use a block size of 1 to be able skip.

This patch reworks the extraction scripts to be much faster and
efficient by reading and writing the calibration data in possibly
one big block.

before: (Tested on a RT-AC58U, which has SPI-NAND).

 # time dd if=/dev/ubi0_1 of=/lib/firmware/... bs=1 skip=4096 count=12064
12064+0 records in
12064+0 records out
real    0m 0.28s
user    0m 0.02s
sys     0m 0.24s

after:

 # time dd if=/dev/ubi0_1 of=/lib/firmware/... bs=12064 skip=4096 count=1 iflag=skip_bytes
1+0 records in
1+0 records out
real    0m 0.01s
user    0m 0.00s
sys     0m 0.00s

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>