Bionic update to v4.14.12 stable release

SRU Justification

    Impact:
       The upstream process for stable tree updates is quite similar
       in scope to the Ubuntu SRU process, e.g., each patch has to
       demonstrably fix a bug, and each patch is vetted by upstream
       by originating either directly from a mainline/stable Linux tree or
       a minimally backported form of that patch. The v4.14.12 upstream stable
       patch set is now available. It should be included in the Ubuntu
       kernel as well.

       git://git.kernel.org/

    TEST CASE: TBD

       The following patches from the v4.14.12 stable release shall be applied:

exec: Weaken dumpability for secureexec
capabilities: fix buffer overread on very short xattr
x86/cpu, x86/pti: Do not enable PTI on AMD processors
x86/pti: Make sure the user/kernel PTEs match
x86/dumpstack: Fix partial register dumps
x86/dumpstack: Print registers for first stack frame
x86/pti: Switch to kernel CR3 at early in entry_SYSCALL_compat()
x86/process: Define cpu_tss_rw in same section as declaration
Revert "xfrm: Fix stack-out-of-bounds read in xfrm_state_find."
rtc: m41t80: m41t80_sqw_set_rate should return 0 on success
rtc: m41t80: fix m41t80_sqw_round_rate return value
rtc: m41t80: avoid i2c read in m41t80_sqw_recalc_rate
rtc: m41t80: avoid i2c read in m41t80_sqw_is_prepared
rtc: m41t80: remove unneeded checks from m41t80_sqw_set_rate
Linux 4.14.12