Reduce BL2 size for FVP

This patch reduces BL2 size by 12kB. Thanks to the shared Mbed TLS heap
between BL1 and BL2, BL2 now requires less memory since it doesn't need
to allocate a heap anymore.

Change-Id: I58a15f8c424273650c9f55112abe88105b6cdbae
Signed-off-by: John Tsichritzis <john.tsichritzis@arm.com>

include/plat/arm/board/common/board_arm_def.h

@@ -102,7 +102,7 @@
  * little space for growth.
  */
 #if TRUSTED_BOARD_BOOT
-# define PLAT_ARM_MAX_BL2_SIZE		0x1F000
+# define PLAT_ARM_MAX_BL2_SIZE		0x1C000
 #else
 # define PLAT_ARM_MAX_BL2_SIZE		0x11000
 #endif