tcpc: Check battery present to enable PD_SUSPEND
tcpc: Check battery present to enable PD_SUSPEND

When doing TCPC firmware update, it suspends the PD port. There is
a check to make sure if the battery level is enough for the update
process. But when no battery presents, it still does the update.
Should also check the battery present. Otherwise, the update
process will make the power lost and result a reboot loop.

BRANCH=none
BUG=b:117498337
TEST=Do TCPC firmware update on the charging port and no battery:
Saw AP console:
  Protect aux fw 0
  Update aux fw 1
  ps8751.1: PD_SUSPEND busy! Could be only power source.
  Protect aux fw 1
Saw EC console:
  [9.165306 C1: Cannot suspend for upgrade, no battery!]

TEST=Do TCPC firmware update on the charging port and battery plugged:
Saw AP console:
  Protect aux fw 0
  Update aux fw 1
  ps8751.1: found SPI flash ID 0x1c11
  ps8751.1: erased 20KB in 434ms
  ps8751.1: verified 0KB in 0s
  ps8751.1: programming 20KB...

Change-Id: I4ed3929d3234d115596f04245e698de8b1b3e662
Signed-off-by: Wai-Hong Tam <04b587fdf5845741a0c5a8b9cd59ca72d73ef8fc@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1271257
Reviewed-by: Furquan Shaikh <6be5c96c464778f89679b1062a2e0a6af93d2aa5@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec