Revert "nvmem: core: add NVMEM_SYSFS Kconfig"

This reverts commit 48dc3910.
To maintain the sequence with other upstream changes of nvmem
framework, reverting now and cherry-pick at later point
of time.

Change-Id: I049bc307156bfc7c066808326e4178f733f080be
Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>