pcmcia: lubbock: fix sockets configuration

On lubbock board, the probe of the driver crashes by dereferencing very
early a platform_data structure which is not set, in
pxa2xx_configure_sockets().

The stack fixed is :
[    0.244353] SA1111 Microprocessor Companion Chip: silicon revision 1, metal revision 1
[    0.256321] sa1111 sa1111: Providing IRQ336-390
[    0.340899] clocksource: Switched to clocksource oscr0
[    0.472263] Unable to handle kernel NULL pointer dereference at virtual address 00000004
[    0.480469] pgd = c0004000
[    0.483432] [00000004] *pgd=00000000
[    0.487105] Internal error: Oops: f5 [#1] ARM
[    0.491497] Modules linked in:
[    0.494650] CPU: 0 PID: 1 Comm: swapper Not tainted 4.8.0-rc3-00080-g1aaa68426f0c-dirty #2068
[    0.503229] Hardware name: Intel DBPXA250 Development Platform (aka Lubbock)
[    0.510344] task: c3e42000 task.stack: c3e44000
[    0.514984] PC is at pxa2xx_configure_sockets+0x4/0x24 (drivers/pcmcia/pxa2xx_base.c:227)
[    0.520193] LR is at pcmcia_lubboc...