stm32/nimble_hci_uart.c: Prevent scheduler running during CYW-BT wakeup.
stm32/nimble_hci_uart.c: Prevent scheduler running during CYW-BT wakeup.

Using mp_hal_delay_ms allows the scheduler to run, which might result in
another transmit operation happening, which would bypass the sleep (and
fail).  Use mp_hal_delay_us instead.

bvernoux/micropython,henriknelson/micropython,pramasoul/micropython,pozetroninc/micropython,pramasoul/micropython,tobbad/micropython,pramasoul/micropython,selste/micropython,tobbad/micropython,kerneltask/micropython,MrSurly/micropython,adafruit/circuitpython,kerneltask/micropython,kerneltask/micropython,kerneltask/micropython,kerneltask/micropython,trezor/micropython,pozetroninc/micropython,henriknelson/micropython,adafruit/circuitpython,adafruit/circuitpython,pramasoul/micropython,bvernoux/micropython,henriknelson/micropython,selste/micropython,selste/micropython,tobbad/micropython,adafruit/circuitpython,MrSurly/micropython,pozetroninc/micropython,tobbad/micropython,tobbad/micropython,selste/micropython,MrSurly/micropython,pramasoul/micropython,pozetroninc/micropython,trezor/micropython,adafruit/circuitpython,henriknelson/micropython,henriknelson/micropython,bvernoux/micropython,bvernoux/micropython,MrSurly/micropython,selste/micropython,bvernoux/micropython,trezor/micropython,adafruit/circuitpython,trezor/micropython,pozetroninc/micropython,MrSurly/micropython,trezor/micropython