common: button: Add items to .bss.slow.
common: button: Add items to .bss.slow.

BUG=chrome-os-partner:46056
BUG=chrome-os-partner:46063
BRANCH=None
TEST=Enable CONFIG_REPLACE_LOADER_WITH_BSS_SLOW on GLaDOS.  Build,
flash, and verify EC and AP boot.  Press power buttons, volume buttons,
and verify all functional.
TEST='sysjump rw' and repeat the above tests.
TEST=make -j buildall tests

CQ-DEPEND=CL:311209

Change-Id: I5dfb9003e2da1660400c04938b4f3106817ffc02
Signed-off-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@google.com>
Reviewed-on: https://chromium-review.googlesource.com/311412
Commit-Ready: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>
Tested-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

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