ntb_hw_switchtec: fix logic error

Newer gcc (version 7 and 8 presumably) warn about a statement mixing
the << operator with logical and:

drivers/ntb/hw/mscc/ntb_hw_switchtec.c: In function 'switchtec_ntb_init_sndev':
drivers/ntb/hw/mscc/ntb_hw_switchtec.c:888:24: error: '<<' in boolean context, did you mean '<' ? [-Werror=int-in-bool-context]

My interpretation here is that the author must have intended a bitmask
rather than a comparison, so I'm changing the '&&' to '&', which makes
a lot more sense in the context.

Fixes: 1b249475275d ("ntb_hw_switchtec: Allow using Switchtec NTB in multi-partition setups")
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jon Mason <jdmason@kudzu.us>