Fix 'writeable' typos

We have about 30 instances of the typo/variant spelling 'writeable',
and over 500 of the more common 'writable'.  Standardize on the
latter.

Change produced with:

  sed -i -e 's/\([Ww][Rr][Ii][Tt]\)[Ee]\([Aa][Bb][Ll][Ee]\)/\1\2/g' $(git grep -il writeable)

and then hand-undoing the instance in linux-headers/linux/kvm.h.

Most of these changes are in comments or documentation; the
exceptions are:
 * a local variable in accel/hvf/hvf-accel-ops.c
 * a local variable in accel/kvm/kvm-all.c
 * the PMCR_WRITABLE_MASK macro in target/arm/internals.h
 * the EPT_VIOLATION_GPA_WRITABLE macro in target/i386/hvf/vmcs.h
   (which is never used anywhere)
 * the AR_TYPE_WRITABLE_MASK macro in target/i386/hvf/vmx.h
   (which is never used anywhere)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Message-id: 20220505095015.2714666-1-peter.maydell@linaro.org

accel/tcg/user-exec.c

@@ -101,10 +101,10 @@ MMUAccessType adjust_signal_pc(uintptr_t *pc, bool is_write)
  * Return true if the write fault has been handled, and should be re-tried.
  *
  * Note that it is important that we don't call page_unprotect() unless
- * this is really a "write to nonwriteable page" fault, because
+ * this is really a "write to nonwritable page" fault, because
  * page_unprotect() assumes that if it is called for an access to
- * a page that's writeable this means we had two threads racing and
- * another thread got there first and already made the page writeable;
+ * a page that's writable this means we had two threads racing and
+ * another thread got there first and already made the page writable;
  * so we will retry the access. If we were to call page_unprotect()
  * for some other kind of fault that should really be passed to the
  * guest, we'd end up in an infinite loop of retrying the faulting access.