fix 2 typos

Booting/linux-bootstrap-3.md

@@ -299,7 +299,7 @@ io_delay();
 
 At first, there is an inline assembly statement with a `cli` instruction which clears the interrupt flag (`IF`). After this, external interrupts are disabled. The next line disables NMI (non-maskable interrupt).
 
-An interrupt is a signal to the CPU which is emitted by hardware or software. After getting such a signal, the CPU suspends the current instruction sequence, saves its state and transfers control to the interrupt handler. After the interrupt handler has finished it's work, it transfers control back to the interrupted instruction. Non-maskable interrupts (NMI) are interrupts which are always processed, independently of permission. They cannot be ignored and are typically used to signal for non-recoverable hardware errors. We will not dive into the details of interrupts now but we will be discussing them in the coming posts.
+An interrupt is a signal to the CPU which is emitted by hardware or software. After getting such a signal, the CPU suspends the current instruction sequence, saves its state and transfers control to the interrupt handler. After the interrupt handler has finished its work, it transfers control back to the interrupted instruction. Non-maskable interrupts (NMI) are interrupts which are always processed, independently of permission. They cannot be ignored and are typically used to signal for non-recoverable hardware errors. We will not dive into the details of interrupts now but we will be discussing them in the coming posts.
 
 Let's get back to the code. We can see in the second line that we are writing the byte `0x80` (disabled bit) to `0x70` (the CMOS Address register). After that, a call to the `io_delay` function occurs. `io_delay` causes a small delay and looks like:
 
@@ -326,7 +326,7 @@ static int a20_test(int loops)
 
 	saved = ctr = rdfs32(A20_TEST_ADDR);
 
-        while (loops--) {
+	while (loops--) {
 		wrfs32(++ctr, A20_TEST_ADDR);
 		io_delay();	/* Serialize and make delay constant */
 		ok = rdgs32(A20_TEST_ADDR+0x10) ^ ctr;