defconfig: 9615: make HOSTAP part a built-in

For 9x15 the modules are stored in the non-boot partition (system)
This change helps in reducing the system image size by making
hostap driver as part of boot image. With HOSTAP being a module,
it was occuping precious system image space.

Change-Id: If38182db7847f4a94b8eef58156a238df545128e
Acked-by: Prasanth Bhatta <c_bhatta@qca.qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>