[ARM] mmp: fix for variables in uncompress.h being discarded

Due to commit:

    5de813b6  ARM: Eliminate decompressor -Dstatic= PIC hack

The data section will be discarded for the decompressor, thus move the
static variables into BSS section by initializing them at run time.
Reported-by: NJonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: NEric Miao <eric.y.miao@gmail.com>

arch/arm/mach-mmp/include/mach/uncompress.h

@@ -14,7 +14,7 @@
 #define UART2_BASE	(APB_PHYS_BASE + 0x17000)
 #define UART3_BASE	(APB_PHYS_BASE + 0x18000)
 
-static volatile unsigned long *UART = (unsigned long *)UART2_BASE;
+static volatile unsigned long *UART;
 
 static inline void putc(char c)
 {
@@ -37,6 +37,9 @@ static inline void flush(void)
 
 static inline void arch_decomp_setup(void)
 {
+	/* default to UART2 */
+	UART = (unsigned long *)UART2_BASE;
+
 	if (machine_is_avengers_lite())
 		UART = (unsigned long *)UART3_BASE;
 }