xtensa: Remove local no-op dram_init_banksize()

When this no-op dram_init_banksize() is removed, the weak default will
be used instead, which correctly sets the bi_dram[] banksize values.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Ovidiu Panait <ovidiu.panait@windriver.com>

board/cadence/xtfpga/xtfpga.c

@@ -49,11 +49,6 @@ int checkboard(void)
 	return 0;
 }
 
-int dram_init_banksize(void)
-{
-	return 0;
-}
-
 int board_postclk_init(void)
 {
 	/*