remove zone identifier

...argets/TARGET_NXP/TARGET_LPC176X/pinmap.c:Zone.Identifier

...gets/TARGET_NXP/TARGET_LPC176X/port_api.c:Zone.Identifier

...ts/TARGET_NXP/TARGET_LPC176X/pwmout_api.c:Zone.Identifier

...rgets/TARGET_NXP/TARGET_LPC176X/rtc_api.c:Zone.Identifier

...ts/TARGET_NXP/TARGET_LPC176X/serial_api.c:Zone.Identifier

...targets/TARGET_NXP/TARGET_LPC176X/sleep.c:Zone.Identifier

...rgets/TARGET_NXP/TARGET_LPC176X/spi_api.c:Zone.Identifier

...ets/TARGET_NXP/TARGET_LPC176X/us_ticker.c:Zone.Identifier

mbed-os/targets/TARGET_NXP/mbed_rtx.h:Zone.Identifier