sfxge: select whether to read current or backup partition in Medford A/B scheme The dynamic config on Medford is stored using two partitions in flash, and at any time one is the 'current' partition, used to provide the active config, and the other 'backup' partition is used for writes. This means that there are two potential partitions that can be used to service reads, and which is required can depend on, for example, whether the read is to get the current contents or to verify a write. When the partition write lock is held, the default behaviour is to read from the backup partition, which was wrong for most reads in the common code which require the current partition. This change allows the current partition to be read whilst the write lock is held. There is one read in Manftest which needs the backup partition. ef10_nvram_partn_read_mode() is created to avoid changing ef10_nvram_partn_read() which shares a prototype with the equivalent Falcon and Siena methods. MC_CMD_NVRAM_READ_IN_V2 adds an extra field, but firmware which doesn't support it just ignores it. Submitted by: Mark Spender <mspender at solarflare.com> Sponsored by: Solarflare Communications, Inc.