wimax/i2400m/sdio: clear the INTR status bit after reading size

In order to avoid issues during high-load traffic, the interrupt
status register has to be cleared ONLY after the RX size is read.

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