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

docs/specs/vmgenid.txt

@@ -153,7 +153,7 @@ change the contents of the memory at runtime, specifically when starting a
 backed-up or snapshotted image.  In order to do this, QEMU must know the
 address that has been allocated.
 
-The mechanism chosen for this memory sharing is writeable fw_cfg blobs.
+The mechanism chosen for this memory sharing is writable fw_cfg blobs.
 These are data object that are visible to both QEMU and guests, and are
 addressable as sequential files.
 
@@ -164,7 +164,7 @@ Two fw_cfg blobs are used in this case:
 /etc/vmgenid_guid - contains the actual VM Generation ID GUID
                   - read-only to the guest
 /etc/vmgenid_addr - contains the address of the downloaded vmgenid blob
-                  - writeable by the guest
+                  - writable by the guest
 
 
 QEMU sends the following commands to the guest at startup: