nvram: increase NVRAM size to 64 KiB

nvram: increase NVRAM size to 64 KiB

For years Broadcom devices use 64 KiB NVRAM partition size and some of
them indeed have it filled in more than 50%. This change allows handling
whole NVRAM e.g. on Netgear WNDR4500 and Netgear R8000.

The same fix was applied to kernel in upstream commit 6ab7c29.

Reported-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
SVN-Revision: 45566