Add more detail to the ubsec(4) note and fix a typo.

Reported by:	linimon

website/content/en/releases/13.0R/relnotes.adoc

@@ -250,7 +250,7 @@ As part of this, the amd64-specific `ACPI_DMAR` kernel option has been
 renamed to `IOMMU`.
 gitref:6186bfbd1880[repository=src] {{< sponsored "DARPA" >}} {{< sponsored "AFRL" >}}
 
-A driver for Arm System Memory Management Unity version 3.2 has been added
+A driver for Arm System Memory Management Unit version 3.2 has been added
 to the aarch64 architecture.
 The driver is enabled by the `IOMMU` kernel option.
 gitref:4cc8701067e1[repository=src] {{< sponsored "DARPA" >}} {{< sponsored "AFRL" >}} {{< sponsored "Innovate UK" >}}
@@ -291,8 +291,9 @@ Several network drivers for obsolete Ethernet adapters have been removed:
 * man:wb[4] Winbond W89C840F gitref:02fae06a11b4[repository=src]
 * man:xe[4] Xircom PCMCIA gitref:7a582e5374c8[repository=src]
 
-The man:ubsec[4] driver has been removed.
-gitref:883a2dc67213[repository=src] {{< sponsored "Chelsio Communications" >}}
+The man:ubsec[4] driver for obsolete Broadcom BCM58xx crypto accelerators
+has been removed.
+gitref:97e251327f95[repository=src] {{< sponsored "Chelsio Communications" >}}
 
 A new man:safexcel[4] driver supports cryptographic requests via the EIP-97
 packet processing module found on the ESPRESSObin.  gitref:b356ddf07671[repository=src] {{< sponsored "Rubicon Communications, LLC" >}}