linux-fslc-imx: update to v5.15.48

Kernel repository has been upgraded up to v5.15.48 from stable korg.

Following upstream commits are included in this version:
----
e1dd58c995da Linux 5.15.48
147ae04a7c52 x86/speculation/mmio: Print SMT warning
59d665a709b0 KVM: x86/speculation: Disable Fill buffer clear within guests
ebd0f558b480 x86/speculation/mmio: Reuse SRBDS mitigation for SBDS
30120b433c1f x86/speculation/srbds: Update SRBDS mitigation selection
531eb5fe3171 x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data
2044838ab228 x86/speculation/mmio: Enable CPU Fill buffer clearing on idle
407d97b99f27 x86/bugs: Group MDS, TAA & Processor MMIO Stale Data mitigations
d74f4eb1ddf0 x86/speculation/mmio: Add mitigation for Processor MMIO Stale Data
8b9521e71179 x86/speculation: Add a common function for MD_CLEAR mitigation update
d822b10f97f6 x86/speculation/mmio: Enumerate Processor MMIO Stale Data bug
1fcc3d646f0b Documentation: Add documentation for Processor MMIO Stale Data
----

Link: https://lore.kernel.org/r/20220614183720.512073672@linuxfoundation.org # v5.15.48
Link: https://github.com/Freescale/linux-fslc/pull/587