ps8740: Make revision check a minimum instead of explicit value
ps8740: Make revision check a minimum instead of explicit value

With a new PS8740 chip revision 0xb the explicit check for 0xa
is failing.  Change this to allow revisions >= 0xa to pass.

BUG=chrome-os-partner:46728
BRANCH=none
TEST=boot on chell and confirm lack of mux init errors

Change-Id: I0847bb9953920569922183ed4c83da2370ef40e4
Signed-off-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/307932
Reviewed-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>

akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec