ARM: qemu-arm: Increase CONFIG_SYS_CBSIZE

CONFIG_SYS_CBSIZE determines the maximum length of the kernel command
line, and the default value of 256 is too small for booting some Linux
images in the wild.
Signed-off-by: NTuomas Tynkkynen <tuomas.tynkkynen@iki.fi>

include/configs/qemu-arm.h

@@ -47,4 +47,6 @@
 	"ramdisk_addr_r=0x44000000\0" \
 	BOOTENV
 
+#define CONFIG_SYS_CBSIZE 512
+
 #endif /* __CONFIG_H */