If barebox is not used as the MLO, then it crashes during boot
with the below error message:

Board: Texas Instrument's Panda
PandaBoard Revision: 003
omap-hsmmc@mci0: registered as mci0
unable to handle paging request at address 0x4a064010
pc : [<8f01e820>]    lr : [<8f0049a0>]
sp : 8cffff80  ip : 00000016  fp : 00100103
r10: 00000000  r9 : 00000ae7  r8 : 4030b76c
r7 : 40300200  r6 : e28f8028  r5 : 0000003e  r4 : 00000000
r3 : 4a064000  r2 : 00000014  r1 : 00000001  r0 : 00000001
Flags: nzCv  IRQs off  FIQs off  Mode SVC_32
[<8f01e820>] (panda_devices_init+0x17c/0x1e0) from [<8f006300>] (start_barebox+0x18/0x10c)
[<8f006300>] (start_barebox+0x18/0x10c) from [<8200006c>] (0x8200006c)

[<8f021248>] (unwind_backtrace+0x0/0x98) from [<8f011a00>] (panic+0x28/0x3c)
[<8f011a00>] (panic+0x28/0x3c) from [<8f02171c>] (do_exception+0x10/0x14)
[<8f02171c>] (do_exception+0x10/0x14) from [<8f021784>] (do_data_abort+0x2c/0x38)
[<8f021784>] (do_data_abort+0x2c/0x38) from [<8f021470>] (data_abort+0x50/0x60)

This is because the USBHOST module is not enabled. The module enable
is is normally done in mach-omap/xload.c which never gets called.

Since we're configuring the USBHOST CLKCTRL register in the board file
anyway, we might as well explicitly enable the module in the same place.

Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>