usb: host: tegra: remove pointless NULL check in tegra_ehci_remove()

Test for tegra and hcd in tegra_ehci_remove() look like potential
NULL pointer dereference, but in fact those tests are not needed,
so remove these pointless tests entirely.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>