Increase UART output buffer on STM32L
Increase UART output buffer on STM32L

STM32L has 16KB RAM, so can use a bigger output buffer.

BUG=chrome-os-partner:18657
BRANCH=none
TEST=boot pit, look at EC console output; shouldn't drop output

Change-Id: I8a3c7ff2923fd815eff748a898dc873f5d86b46c
Signed-off-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/49332
Reviewed-by: Bill Richardson <129945214b1d548d8e49b6c29c43094f8c78057f@chromium.org>

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