nyan: switch chip variant to STM32L100RBT6
nyan: switch chip variant to STM32L100RBT6

The new boards will be populated with STM32L100RBT6,
so let's update the CHIP_VARIANT accordingly.
This is backward-compatible with the STM32L151RBT6 which is soldered on
older boards (it just doesn't use the full memory).

Signed-off-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

BRANCH=none
BUG=none
TEST=boot the system on Nyan reworked with STM32L100RBT6

Change-Id: I73a4c587c7dc3646777166606e06f3dfaed2400c
Reviewed-on: https://chromium-review.googlesource.com/173633
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-by: Vic Yang <5fd92abeee651458f98e2856f4f200ee971cee4d@chromium.org>
Tested-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Commit-Queue: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Commit-Queue: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

alterapraxisptyltd/chromium-ec,fourier49/BZ_DEV_EC,thehobn/ec,fourier49/BIZ_EC,longsleep/ec,fourier49/BZ_DEV_EC,alterapraxisptyltd/chromium-ec,fourier49/BZ_DEV_EC,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,gelraen/cros-ec,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,eatbyte/chromium-ec,coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,longsleep/ec,eatbyte/chromium-ec,thehobn/ec,gelraen/cros-ec,fourier49/BIZ_EC,longsleep/ec,md5555/ec,coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,thehobn/ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BIZ_EC,md5555/ec,mtk09422/chromiumos-platform-ec,longsleep/ec,thehobn/ec,gelraen/cros-ec,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,gelraen/cros-ec,eatbyte/chromium-ec,coreboot/chrome-ec,mtk09422/chromiumos-platform-ec,mtk09422/chromiumos-platform-ec,fourier49/BIZ_EC,eatbyte/chromium-ec,md5555/ec,coreboot/chrome-ec