post/drivers/i2c.c: fix compile error

Commit 7e263cea "post/i2c: Clean up detection logic" added a "const"
qualifier to the declaration of i2c_addr_list[], missing the fact that
the list gets modified later in the code, which results in build
errors like these:

i2c.c: In function 'i2c_post_test':
i2c.c:88: error: assignment of read-only location

Remove the incorrect "const".

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Peter Tyser <ptyser@xes-inc.com>
Cc: Heiko Schocher <hs@denx.de>
Acked-by: Heiko Schocher <hs@denx.de>

post/drivers/i2c.c

@@ -74,7 +74,7 @@ int i2c_post_test (int flags)
 #else
 	unsigned int ret  = 0;
 	int j;
-	const unsigned char i2c_addr_list[] = CONFIG_SYS_POST_I2C_ADDRS;
+	unsigned char i2c_addr_list[] = CONFIG_SYS_POST_I2C_ADDRS;
 
 	/* Start at address 1, address 0 is the general call address */
 	for (i = 1; i < 128; i++) {