Disable clang-format for sensitive blocks

Things like macro blocks should not be auto-formatted.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

src/arch/avr/uart.c

@@ -6,6 +6,7 @@
 #include <arch/uart.h>
 #include <board/cpu.h>
 
+// clang-format off
 #define UART(N) \
     { \
         &UCSR ## N ## A, \
@@ -39,6 +40,7 @@
 #else
     #error "Could not find UART definitions"
 #endif
+// clang-format on
 
 int16_t uart_count() {
     return sizeof(UARTS)/sizeof(struct Uart);