pcmcia/at91_cf: don't redefine SZ_2K

This fixes:

	drivers/pcmcia/at91_cf.c:55:1: warning: "SZ_2K" redefined

Since

	c1191b0e ([ARM] Kirkwood: create a mapping for the Security Accelerator SRAM)

SZ_2K is defined in arch/arm/include/asm/sizes.h.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>