USB: Add config option to call ehci_hcd_init() again after EHCI reset

This patch adds the config option CONFIG_EHCI_HCD_INIT_AFTER_RESET
to call ehci_hcd_init() again after ehci_reset() is executed. This
is needed for the upcoming VCT EHCI support which needs to re-init
the hcd part again after the EHCI CMD_RESET is executed.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Remy Bohmer <linux@bohmer.net>