mfd: omap-usb-tll: Remove unused usbtll_readb() function

Clang with W=1 reports:

drivers/mfd/omap-usb-tll.c:128:18: error: unused function
'usbtll_readb' [-Werror,-Wunused-function]
static inline u8 usbtll_readb(void __iomem *base, u32 reg)
^
This function is not used so remove it.

Signed-off-by: Tom Rix <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/mfd/omap-usb-tll.c

···
 	writeb_relaxed(val, base + reg);
 }
 
-static inline u8 usbtll_readb(void __iomem *base, u32 reg)
-{
-	return readb_relaxed(base + reg);
-}
-
 /*-------------------------------------------------------------------------*/
 
 static bool is_ohci_port(enum usbhs_omap_port_mode pmode)