Fix R29 not getting zeroed in both PRU asm files

Signed-off-by: Kumar Abhishek <abhishek@theembeddedkitchen.net>
[pru1fw.asm]: Shift sample bank from R4-R11 to R14-R21 (possibly till R29)

Signed-off-by: Kumar Abhishek <abhishek@theembeddedkitchen.net>
PRU Sampling now working at 100MHz.

Signed-off-by: Kumar Abhishek <abhishek@theembeddedkitchen.net>