pd: allow new power request if the max voltage has changed
pd: allow new power request if the max voltage has changed

The current power request function avoids redundant requests by
checking if we have previously requested vSafe5V or the max we
can request. But, if the max voltage that we can request changes,
then sending another max request is not redundant. This CL modifies
the request function to check for redundant requests by checking
the max voltage that can be requested, so if the max voltage
changes, then a new request is allowed.

BUG=none
BRANCH=samus
TEST=on pd console:
pd 0 dev 5
pd 0 dev 12
pd 0 dev 20
all send new request immediately.

Change-Id: Ifcdcc3eac9e566714f6dc609e46bbb0b94426499
Signed-off-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/236882
Reviewed-by: Shawn Nematbakhsh <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>

eatbyte/chromium-ec,eatbyte/chromium-ec,fourier49/BIZ_EC,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,fourier49/BZ_DEV_EC,fourier49/BZ_DEV_EC,coreboot/chrome-ec,fourier49/BIZ_EC,fourier49/BIZ_EC,eatbyte/chromium-ec,coreboot/chrome-ec,coreboot/chrome-ec,mtk09422/chromiumos-platform-ec,coreboot/chrome-ec,md5555/ec,mtk09422/chromiumos-platform-ec,md5555/ec,md5555/ec,fourier49/BZ_DEV_EC,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,eatbyte/chromium-ec,fourier49/BIZ_EC,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec