usb: ehci-omap: drop unused ehci_read() function

usb: ehci-omap: drop unused ehci_read() function

After moving the omap1 platform into generalized multiplatform
support on ARM, the kernel test robot points out a W=1 warning that
now shows up in more configurations:

drivers/usb/host/ehci-omap.c:64:19: warning: unused function 'ehci_read'

The function was last used 9 years ago and can just be removed.

Fixes: 87425ad36330 ("USB: ehci-omap: Remove PHY reset handling code")
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20220428102314.950323-1-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>