default or selected kernelversion does not have config value CONFIG_INFINIBAND_EHCA.
Result is shown for kernelversion 6.5.1

eHCA support

modulename: ib_ehca.ko

configname: CONFIG_INFINIBAND_EHCA

Linux Kernel Configuration
└─>Device Drivers
└─>InfiniBand support
└─>eHCA support
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
This driver supports the IBM pSeries eHCA InfiniBand adapter.

To compile the driver as a module, choose M here. The module
will be called ib_ehca.

source code: