ramips: lzma-loader: use proper register names

Before this was reworked, in the file for mt7621 subtarget
(target/linux/ramips/image/lzma-loader/src/board-mt7621.c)
the "Transmitter shift register empty" bit TEMT was used instead of
the "Transmitter holding register empty" bit THRE,
but after the rework, this value was labeled as the THRE bit instead.

Functionally there is no difference, but this is confusing to read,
as it suggests that the subtargets have different bits for the same
register in UART when in reality they are exactly the same.

One can use either bit, or both, at user's descretion
in order to determine whether the UART TX buffer is ready.
The generic kernel early-printk uses both,
(arch/mips/kernel/early_printk_8250.c)
while the ralink-specific early-printk uses only THRE,
(arch/mips/ralink/early_printk.c).

Define both bits and rewrite macros for readability,
keep the same values, as changing which to use should be tested first.

Ref: c31319b66 ("ramips: lzma-loader: Refactor loader")
Signed-off-by: Michael Pratt <[email protected]>

target/linux/ramips/image/lzma-loader/src/board.c

@@ -26,21 +26,24 @@
 #define KSEG0ADDR(a)		(CPHYSADDR(a) | KSEG0)
 #define KSEG1ADDR(a)		(CPHYSADDR(a) | KSEG1)
 
+#define UART_LSR_THRE		0x20
+#define UART_LSR_TEMT		0x40
+
 #if defined(SOC_MT7620) || defined(SOC_RT3883)
 #define UART_BASE			KSEG1ADDR(0x10000c00)
 #define UART_THR			(UART_BASE + 0x04)
 #define UART_LSR			(UART_BASE + 0x1c)
-#define UART_LSR_THRE_MASK	0x40
+#define UART_LSR_MASK			UART_LSR_TEMT
 #elif defined(SOC_MT7621)
 #define UART_BASE			KSEG1ADDR(0x1e000c00)
 #define UART_THR			(UART_BASE + 0x00)
 #define UART_LSR			(UART_BASE + 0x14)
-#define UART_LSR_THRE_MASK	0x20
+#define UART_LSR_MASK			UART_LSR_THRE
 #elif defined(SOC_RT305X)
 #define UART_BASE			KSEG1ADDR(0x10000500)
 #define UART_THR			(UART_BASE + 0x04)
 #define UART_LSR			(UART_BASE + 0x1c)
-#define UART_LSR_THRE_MASK	0x20
+#define UART_LSR_MASK			UART_LSR_THRE
 #else
 #error "Unsupported SOC..."
 #endif
@@ -56,7 +59,7 @@ void board_init(void)
 
 void board_putc(int ch)
 {
-	while ((READREG(UART_LSR) & UART_LSR_THRE_MASK) == 0);
+	while ((READREG(UART_LSR) & UART_LSR_MASK) == 0);
 	WRITEREG(UART_THR, ch);
-	while ((READREG(UART_LSR) & UART_LSR_THRE_MASK) == 0);
+	while ((READREG(UART_LSR) & UART_LSR_MASK) == 0);
 }