Rename NB_PORTS as EHCI_PORTS to avoid definition clash
with UHCI equivalent:
hw/usb/hcd-ehci.h:40:9: error: 'NB_PORTS' macro redefined [-Werror,-Wmacro-redefined]
#define NB_PORTS 6 /* Max. Number of downstream ports */
^
hw/usb/hcd-uhci.h:38:9: note: previous definition is here
#define NB_PORTS 2
^
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>