Improved sys access to LPTC registers

Erik von Reisrequested to merge
erik.vonreis/advligorts:write_to_lptc into master

Advanced timing registers exposed to sys file system. Also accessor functions created in the driver.

Add write support for writeable registers in the sys filesystem.

echo nnn > /sys/kernel/gpstime/lptc/regname

nnn can be decimal 0xhex, 0octal, or 0bbinary.

referecne DCC doc T2000406 for register meanings

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