mwifiex: fix copy-n-paste 'thinko' for tsf_val

  CC [M]  drivers/net/wireless/mwifiex/join.o
drivers/net/wireless/mwifiex/join.c: In function ‘mwifiex_cmd_802_11_associate’:
drivers/net/wireless/mwifiex/join.c:119:8: warning: ‘tsf_val’ may be used uninitialized in this function
drivers/net/wireless/mwifiex/join.c:103:12: note: ‘tsf_val’ was declared here

Looks like a copy-n-paste error, identical lines are a few lines below
the ones removed, with an actual memcpy to tsf_val in between...

Signed-off-by: John W. Linville <linville@tuxdriver.com>