wimax/i2400m: Make boot retries a BUS-specific parameter

In i2400m-based devices, the driver's bootloader will retry to load
the firmware when things go wrong. The driver currently has a constant
(I2400M_BOOT_RETRIES) which governs the max number of tries.

However, different SKUs of the same hardware may admit or require
different numbers of retries due to it's particulars, so it is made a
BUS specific parameter and different values are assigned for 5x50
devices versus the 3200 ones.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Signed-off-by: Cindy H Kao <cindy.h.kao@intel.com>
Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>