boards: st: nucleo_wba55cg: define all LEDs and buttons

This board includes three gpio-connected LEDs and push-buttons. Include
all missing defines in board's DTS and while at it, fix existing button
definition (missing pull-up enable) and align node names with other
boards (e.g. 'nucleo_wb55rg').

Provided changes were tested on real board with 'blinky' and 'button'
samples.

Additionally, duplicated LED nodes no longer required were removed from
overlay file for this board, in 'suspend_to_ram' sample.

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>