sfc: initialise found bitmap in efx_ef10_mtd_probe

[ Upstream commit c65285428b6e7797f1bb063f33b0ae7e93397b7b ]

The bitmap of found partitions in efx_ef10_mtd_probe was not
initialised, causing partitions to be suppressed based off whatever
value was in the bitmap at the start.

Fixes: 3366463513f5 ("sfc: suppress duplicate nvmem partition types in efx_ef10_mtd_probe")
Signed-off-by: Bert Kenward <bkenward@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>