Update to v6.3 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-6.3

Test: Bionic unit tests pass.
Change-Id: I5270ef291a77343e47ef3a5fbd02b8cacf218ec5
diff --git a/libc/kernel/uapi/linux/serial_reg.h b/libc/kernel/uapi/linux/serial_reg.h
index e41e649..36d778d 100644
--- a/libc/kernel/uapi/linux/serial_reg.h
+++ b/libc/kernel/uapi/linux/serial_reg.h
@@ -37,6 +37,11 @@
 #define UART_IIR_RX_TIMEOUT 0x0c
 #define UART_IIR_XOFF 0x10
 #define UART_IIR_CTS_RTS_DSR 0x20
+#define UART_IIR_64BYTE_FIFO 0x20
+#define UART_IIR_FIFO_ENABLED 0xc0
+#define UART_IIR_FIFO_ENABLED_8250 0x00
+#define UART_IIR_FIFO_ENABLED_16550 0x80
+#define UART_IIR_FIFO_ENABLED_16550A 0xc0
 #define UART_FCR 2
 #define UART_FCR_ENABLE_FIFO 0x01
 #define UART_FCR_CLEAR_RCVR 0x02