hwmon: qti_amoled_ecm: add debug log for nvmem writes

Add a wrapper function ecm_nvmem_device_write() which can log
the nvmem writes. This is useful for debugging.

Change-Id: Icc4ee6ff50b46f92e0169660e3400d80f7d4da37
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>